110706 faculty position paper on vmat-web

8/13/2019 110706 Faculty Position Paper on VMAT-Web

1/36

FACULTY OF RADIATION ONCOLOGY

THE ROYAL AUSTRALIAN AND NEW ZEALAND COLLEGE OF RADIOLOGISTS

POSITION PAPER

THE EVIDENCE BASE FOR MULTIPLE

VOLUMETRIC MODULATED ARC THERAPY (VMAT)

- A QUALITY PERSPECTIVE


2/36

Name of document and version:

Faculty of Radiation Oncology, Position Paper: The Evidence Base for Multiple Volumetric Modulated Arc

Therapy (VMAT) A Quality Perspective, version 1

Approved by:

Faculty of Radiation Oncology Board

Date of approval:

20 May 2011

ABN 37 000 029 863

Copyright for this publication rests with The Royal Australian and New Zealand College of Radiologists

The Royal Australian and New Zealand College of Radiologists

Level 9, 51 Druitt Street

Sydney NSW 2000

Australia

Email: [email protected]

Website: www.ranzcr.edu.au

Telephone: +61 2 9268 9777

Facsimile: +61 2 9268 9799

Disclaimer: The information provided in this document is of a general nature only and is not intended as

a substitute for medical or legal advice. It is designed to support, not replace, the relationship that exists

between a patient and his/her doctor.


3/36

TABLE OF CONTENTS

Objectives 2

Executive Summary 2

Background 3

Volumetric Modulated Arc Therapy (VMAT) 3

Faculty of Radiation Oncology Position 4

Bibliography Introduction 5

Appendix I: the Historical and Technical background to VMAT 6

Technical History 6

What is HT? 7

What is VMAT? 7

Single arc or Multiple Arc 10

VMAT Treatment delivery times 11

Radiobiological considerations 12

Head and Neck treatments 12

Prostate 12

Breast 13

Lung 14

Brain 15

Other clinical applications 16

Quality Assurance 16

Comparison of Helical Tomotherapy and VMAT techniques 16

Conclusions 17

Bibliography Appendix I 18

Appendix II: Detailed evidence for the benets of single and multi arc VMAT 20

Bibliography Appendix II 30

Acknowledgments 32

Acronyms and Abbreviations 33


4/36

THE FACULTY OF RADIATION ONCOLOGY, RANZCR,is the peak bi-national body advancing patient

care and the specialty of Radiation Oncology through setting of quality standards, producing excellent

Radiation Oncology specialists, and driving research, innovation and collaboration in the treatment of

cancer.

VISION

To have an innovative, world class Radiation Oncology Specialty for Australia and New Zealand

focused on patient needs and quality.

OUR VALUES

In undertaking our activities and in managing the way we interact with our Fellows, trainees,

members, staff, stakeholders, the community and all others with whom we liaise, the Faculty of

Radiation Oncology, RANZCR, will demonstrate the following values:

Quality of Care - performing to and upholding high standards Integrity, honesty and propriety - upholding professional and ethical values

Patient orientation - understanding and reecting the views of Fellows and members and working

with them to achieve the best outcomes

Fiscal responsibility and efciency - using the resources of the College prudently.

OUR PROMISE TO THE PATIENTS

We will advocate for the best possible care for individual patients in multidisciplinary meetings and for

all patients with government.

OUR PROMISE TO TRAINEES

We ensure the highest standard of training in radiation oncology by combining a world-class

curriculum with passionate and supportive supervisors. The voice of trainees is valued in Radiation

Oncology.

OUR PROMISE TO OUR FELLOWS

We are a member based organisation that utilises its resources effectively and strategically to full our

vision, purpose and core objectives. We strive for best practice and facilitate life-long learning of our

members.

OUR PROMISE TO OUR PARTNERS & STAKEHOLDERS

We are a transparent and collaborative organisation that strives to promote partnerships and

participation of all relevant stakeholders to ensure that patients across Australia and New Zealand

receive a high-quality, timely and appropriate level of care.


5/36

TheEvidenceBaseforMultipleVolumetricModulatedArcTherapy

FacultyofRadiationOncology

3

OBJECTIVES

This Position Paper summarises the current evidence (as of 2011) around both Single and

Multiple dynamic arc therapy also known as Volumetric Modulated Arc Therapy (VMAT). The

aim of the paper is to inform cancer professionals, consumers and interested individuals and to

put forward a quality-focused perspective.

Appendix I: Provides the historical and technical background to VMAT

Appendix II: Provides detailed contemporary international evidence for the benets of Single

and Multi arc Radiotherapy.

EXECUTIVE SUMMARY

There is a very largebody of evidence demonstrating that Single or Multi-arc therapy:

1. Achieves superior target dose quality(homogeneity and adjacent normal tissue sparing) in

a range of tumour sites when compared to multi- eld step and shoot IMRT, particularly for

complex targets with adjacent organs at risk.

2. Consistently requireslowerradiation doses (Monitor Unit output) than step and shoot IMRT

3. Consistently achieves much shortertreatment times than step and shoot IMRT

4. Provides more efcientRT treatment delivery

5. Is more comfortablefor the patient

6. Has improved accuracy with IGRT (Image Guided) performance and dosimetry.

There is a very largebody of evidence indicating that an improved therapeutic ratio in clinical

radiotherapy will translate to meaningful improvements in patient outcomes such as overall

survival, disease free survival, reduced toxicity and improved quality of life.

This Position Paper provides signicant evidence that volumetric modulated arc therapy, when

performed with multiple arcs, achieves superior target dose homogeneity and adjacent normal

tissue sparing in a range of tumour sites when compared to 6 eld 3D conformal radiotherapy.

It is, at a minimum, equivalent to the best planned multiple eld IMRT in dosimetric terms and

is considerably more efcient in terms of treatment delivery, with important radiobiological

advantages to the patient, who also benets from reduced discomfort associated with a

reduction in treatment times, particularly for complex volumes such as head and neck sites.


6/36



BACKGROUND

Intensity-modulated radiation therapy (IMRT) produces clinically relevant improved outcomes to

three-dimensional conformal radiotherapy (3DCRT), particularly in patients with concave target

volumes. Two excellent reviews and a large economic analysis of the evidence provide a useful

background to establish without question the real world benets of this technology. (vide infra). It

is therefore important that these new techniques are adopted into mainstream practice.

Around 60 quality studies included three Randomised Controlled Trials (RCTs) in head and

neck cancer (205 patients) and three in breast cancer (664 patients), showed signicant

improvements with IMRT in each trial. A recent meta-analysis collated data from 56 trials

and showed that IMRT can reduce toxicities when compared to non-IMRT treatments. Data

relating to overall survival and local control are inconclusive at this time. Incremental gains in

radiotherapy therapeutic ratio and reductions in toxicity may still require very large studies to

show survival differences. Toxicity reduction in its own right, is an appropriate outcome measure

worthy of use as a benchmark for implementation of a particular technique. Reductions in

toxicity lead to improved quality of life and reduced health costs.

There have been approximately 70-80 additional non-randomised studies in head and neck

cancer, prostate cancer, breast cancer and other tumour sites. Again they report benets in

acute and late toxicity, health-related quality of life and tumour control end points. A further 30

unpublished, ongoing or planned RCTs incorporating IMRT are currently in progress. These

studies have reported improved target coverage, and lower doses to adjacent organs-at-risk

for CNS tumours, head and neck (H&N), upper abdominal and pelvic cancers. IMRT in the

treatment of H&N cancer reduces parotid doses, resulting in less xerostomia and improved

quality-of-life. In the dose-escalated treatment of localized prostate cancer, reduced rates of

acute gastrointestinal toxicity have been reported after IMRT treatment with a simultaneous

integrated boost (SIB) technique compared to a sequential boost technique with 3D-CRT.

In addition to these direct approaches, there are hundreds of studies using indirect techniques.

This involves the correlation of the improved dose-volume constraints that were achievable with

IMRT, with modelled organ function and complication rates. For many organs, IMRT studies

have yielded valuable dose-volume-toxicity relations, which are now used as objectives in IMRT

optimisation to avoid organ toxicity.

There are also some possible practical and theoretical disadvantages of IMRT.

Some less experienced units report longer treatment planning processes.

Treatment delivery currently requires extensive physics quality assurance.

The prolonged beam delivery time of IMRT compared to 3D-CRT has the potentialto worsen the accuracy of treatment due to increased intra-fractional patient motion.

Patient throughput is reduced in comparison to 3D-CRT.

There is a higher integral radiation dose to the patient with IMRT.


7/36



5

VOLUMETRIC MODULATED ARC THERAPY (VMAT)

VMAT is a new type of intensity-modulated radiation therapy (IMRT) treatment technique

that uses the same hardware (i.e. a digital linear accelerator) as used for IMRT or conformal

treatment, but delivers the radiotherapy treatment using a rotational or arc geometry rather

than several static beams. A generation ago radiotherapy sometimes used old fashioned arctreatments for spherical tumour sites in the midline of the body (e.g. prostate and pituitary).

These treatments were performed on older linear accelerators (linacs) or even orthovotage

machines and in both their geometry and technical specications bore no effective resemblance

to VMAT apart from the serendipitous use of the word arc. A suitable comparator would be the

use of the words deep x-ray therapy to describe megavoltage radiotherapy.

Recently, volumetric-modulated arc therapy (VMAT) has gained enormous interest world-wide.

This technique uses continuous modulation (i.e. moving the collimator leaves) of the multileaf

collimator (MLC) elds, continuous change of the uence rate (the intensity of the X rays) and

gantry rotation speed across a single or multiple 360 degree rotation(s) (see Appendix I). This

signicantly reduces beam delivery time compared to conventional xed eld IMRT (otherwiseknown as step and shoot IMRT). This has major benets for patient comfort.

VMAT techniques require a lower number of monitor units (i.e. a lower X ray beam intensity and

duration), lessening the risk of accidental overdosage, such has been recently reported in the

recent New York Times articles. VMAT improves doseage homogeneity and sparing of critical

organs over IMRT for many tumour sites (Appendix II).

FACULTY OF RADIATION ONCOLOGY POSITION

Multiple Arc VMAT has signicant dosimetric benets over IMRT or single arc VMAT, particularly

for complex target volumes. Multiple-arc therapy has possible radiobiological advantages over

IMRT as a consequence of the shorter delivery times.

The evidence around VMAT is further enhanced when considered together with a very large

body of International randomized evidence, extending over 15 years (plus), demonstrating the

axiom that improved dosimetry translates into improved tumour control and lower normal toxicity

rates that are clinically meaningful.

It is highly plausible that further improvements in the therapeutic ratio for clinical radiotherapy

for most tumour sites will continue to translate into clinical, cost benet, and cost utility

improvement that are very relevant for patients and the community as a whole.


8/36



BIBLIOGRAPHY INTRODUCTION

S. Hummel, E. L. Simpson, P. Hemingway, M. D. Stevenson, and A. Rees, Intensity-

modulated radiotherapy for the treatment of prostate cancer: a systematic review and economic

evaluation, Health Technology Assessment (Winchester, England), vol. 14, no. 47, pp. 1-108,

iii-iv, Oct. 2010.

J. Staffurth, A review of the clinical evidence for intensity-modulated radiotherapy, Clinical

Oncology (Royal College of Radiologists (Great Britain)), vol. 22, no. 8, pp. 643-657, Oct. 2010.

L. Veldeman, I. Madani, F. Hulstaert, G. De Meerleer, M. Mareel, and W. De Neve, Evidence

behind use of intensity-modulated radiotherapy: a systematic review of comparative clinical

studies, The Lancet Oncology, vol. 9, no. 4, pp. 367-375, Apr. 2008.


9/36



7

APPENDIX I: THE HISTORICAL AND TECHNICAL BACKGROUND TO VMAT

TECHNICAL HISTORY

External beam radiotherapy treatments are conventionally given from one or more xed gantry

angles. For deep seated targets with adjacent critical normal tissues such as prostate and its

close proximity to the rectum, or where there is complex geometry, as many as 6-9 beams are

utilized to optimize the geometric dose parameters. Multiple non-conformal beams as many as

12-15 per day are used in complex head and neck plans, with set-up and treatment times not

uncommonly taking 20-30 minutes per day.

Another way of delivering dose in the past has been with a xed rotational arc. To treat a

prostate volume two 155-170 degree arcs were utilized, with the aperture of the beam

shape xed, and the dose rate during uniform gantry rotation also xed. This technique was

popular in some Australian radiotherapy centres treating localized prostate cancer in the mid

to late 1990s as an alternative to the three or four eld box technique most commonly seen

in that era. A tubular Planning Target Volume (PTV), with a circular cross-section was created

using this technique. An MBS item number has stayed on the schedule from that time, withthe wording stating that the re-imbursement for one arc was to be considered the equivalent

of 3 xed beams, and with two arcs planned and treated each day, the treatment attracted re-

imbursement equivalent to six static elds.

Improvements in beam shaping are accomplished using an important accessory called a multi-

leaf collimator (MLC), a device with 80-120 computer-controlled mechanical tungsten leaves

or ngers that move to create apertures of different shapes and sizes. The rst MLC was

introduced into an Australian department in 1995. All new Linear accelerators introduced this

decade incorporate this technology.

Newer radiotherapy planning systems use intensity-modulation with xed beams from multiplegantry angles and a sliding window technique painting dose across the surface of the beam

by its division into multiple smaller beamlets. This is achieved by dynamic MLC leaf motion

sliding across the window of the beam. Beam-on times are typically 40 to 80 seconds per beam,

compared to 10 to 20 seconds for a 3D conformal treatment. There are often an increased

number of static IMRT elds, compared to 3D conformal treatments. These are the two main

contributing factors to the signicantly increased daily treatment time for IMRT treatments.

Intensity Modulated radiation therapy (IMRT) using a conventional linear accelerator equipped

with a MLC was adapted for clinical use to treat prostate cancer in 1995 (ref 1). This was

followed by other treatment sites, including head and neck, brain, and abdomino-pelvic tumours.

A recent meta-analysis collated data from 56 trials showed that IMRT can reduce toxicities

as compared to non-IMRT treatments. Data relating to overall survival and local control areinconclusive at this time (ref 2). However, small incremental gains in radiotherapy therapeutic

ratio and reductions in toxicity may still require very large studies to show survival differences.

One could argue however, that toxicity reduction in its own right, is an appropriate outcome

measure worthy of being used as a benchmark for implementation of a particular technique.

Reductions in toxicity lead to improved quality of life and less cost compared with having to

manage a patients toxicity.

With data accumulating showing the advantages of IMRT, the impetus in the last decade has

been to improve the quality, efciency and accuracy with image guided radiation therapy (IGRT),

as well as the ability to paint dose distributions.

Both Helical Tomotherapy (HT) and Volumetric Modulated Arc Therapy (VMAT) are rotational

radiotherapy modalities that use continuous gantry rotation with dynamic multi-leaf collimation.

HT delivers intensity-modulated fan beams using binary MLC in a helical rotational pattern about


10/36



the patient by translating the patient through the rotating gantry (Tomotherapy Hi-Art System,

Madison, Wisconsin) VMAT, by comparison, uses a conventional linear accelerator (linac) to

deliver radiation in a cone-beam geometry using dynamic MLC, with no couch translation during

the treatment.

WHAT IS HT?

Pioneered by Mackie (ref 22,23) Helical Tomotherapy was made commercially available by

Tomotherapy Inc., and has been used for a wide variety of applications. The rst Tomotherapy

unit in Australia and New Zealand was commissioned in mid 2010. The unit supercially

resembles a CT scanner in that the patient is translated through the central aperture of the

circular unit as it rotates. Each gantry rotation consists of 51 equally spaced beam projections

and 64 binary MLC leaves in each projection. Projection time is limited by gantry speed (15-60

seconds). The degree of intensity modulation is determined by the modulation factor, which

is the maximum leaf open time divided by the average leaf open time. Similar to helical CT

technology, the degree of fan-beam overlapping is determined by the pitch factor, which is the

ratio of couch translation per rotation to the jaw width. In the current software version (version

3.1.4) the jaw width options are 1.0, 2.5 and 5.0cm. The radiation is delivered using a standard

6MV wave guide, very similar to that in a standard linear accelerator.

WHAT IS VMAT?

Volumetric Modulated Arc Therapy (VMAT) is a major advance over xed gantry angle IMRT in

the efciency of delivery of the painted dose.

Volumetric modulated arc therapy (VMAT) proposed by Otto (ref 3) is an Food and Drug

Administration (FDA) approved treatment paradigm, which makes use of conventional current

generation Linear Accelerator as are widely available in Australia. There are three mechanical

variables in VMAT delivery:

Gantry rotation

Multileaf collimator motion, and

Dose rate modulation

Both the MLC aperture and the dose rate can be simultaneously adjusted in an arc of 360

degrees or less, whereas gantry speed is modulated as needed.

During a VMAT treatment, the Linear Accelerator rotates around the patient while the radiation

beam is shaped and reshaped as it is continuously delivered from virtually every angle in a

revolution.

During a VMAT treatment, specialized software algorithms will vary the three parameterssimultaneously: the speed of rotation around the patient, the shape of the MLC aperture, and

the dose delivery rate. The target volume dose does not change when using VMAT. The

amount of scatter and leakage radiation dose to the rest of the body is reduced compared to

conventional IMRT.

VMAT uses a progressive sampling algorithm, which starts sampling from 10 gantry angles,

and then with each level of optimization, the resolution is gradually improved. In the rst level of

optimization, the gap between the 10 gantry angles is 32 degrees, in the second level, there are

21 beams with a gap of 16 degrees, in the third level there are 43 gantry angles with a gap of 8

degrees, in the fourth level there are 87 gantry angles with a gap of 4 degrees and in the 5thand

last level there are 177 gantry angles with a gap of 2 degrees.


11/36



9

Both the MLC position and the monitor units are included as optimization parameters, with a

cost-function based on dose volume constraints of the target and the normal tissues. During

optimization, further constraints are imposed on MLC motion, dose rate, and gantry speed such

that these variables are within the capability of the linac. The optimization process begins with a

small number of points and gradually increases to ensure dose calculation accuracy.

Ottos algorithm has been developed by Varian (Varian Medical Systems, Palo Alto, CA, USA)

and is marketed as RapidArc. The US FDA approved RapidArc for clinical use in February

2008, with rst patients treated in North American centres in May 2008. In its rst released

software version, only one or two full rotation arcs could be planned (Aria software version 8.5).

The early marketing for the Varian VMAT product emphasized the single gantry rotation with the

marketing catch phrase One revolution is all it takes!

In the second software upgrade (Aria version 8.6) released in the rst half of 2009, partial arcs,

arcs with exclusion zones (e.g. so that the entry angle through a metallic hip replacement can

be avoided) and arcs from different gantry angles (e.g. vertex elds for cranial treatments)

allowed greater freedoms of dose intensity modulation for complex target volumes where

adjacent critical normal tissue structures need to be avoided. There are currently more than

200 centres worldwide using this technology, including multiple centres in three Australian

states, with more to follow.

Elekta (Elekta AB, Stockholm, Sweden) also have a product named VMAT, which does not

use Ottos algorithm, but uses a proprietary algorithm. This emphasized multiple arcs from

the earliest software releases, in contrast to the early Varian releases (ref 4). The European

Commission gave regulatory approval to Elekta VMAT in January 2008, with clinical use

commencing in the United Kingdom and Austria the same month. The rst North American

centre went clinical in July 2008, and there are currently more than 200 centres worldwide using

this technology. Multiple centres in Australia and New Zealand are close to going clinical with

this technology.

Early users of both the Varian and Elekta VMAT systems were quick to see the need to

characterize the differences in plan quality, planning time, and delivery time for IMRT and VMAT.

Figure 1:A diagrammatic representation of thegantry angle samples in the rst (darker arrows)

and second resolution levels of VMAT planning

(author)

Figure 2:A diagrammatic representation ofthe 177 gantry angles sampled (2 degree

separations) in the fth resolution level of VMAT

planning algorithm. (picture source Varian users

presentation)


12/36



SINGLE ARC OR MULTIPLE ARC

It was recognized by multiple authors very early on with IMRT that 7 and 9 eld xed gantry

sliding window IMRT plans gave superior dose homogeneity to PTV than seen with 5 eld

treatments, by virtue of greater freedom of intensity modulation from more gantry angles.

Similarly, the concern arose that a single 360-degree arc rotation was insufcient in terms ofdegrees of freedom of modulation for anything but the simplest of targets. Borteld and Webb

wrote a paper questioning the value of single arc treatments, highlighting the planning freedom

constraints for complex targets with adjacent organs at risk (OAR) (ref 9). The criticisms in

their paper, which was submitted for publication in August 2008, were effectively answered by

Verbakel as by that time VMAT was in clinical use in Amsterdam, with VMAT single or double

arc treatments having the variations in dose rate that are possible with the technology that had

not been seen in earlier algorithms (ref 10).

The planning technique for VMAT has evolved with software upgrades.When rst introduced, a

plan using a double arc to treat a 2 Gray PTV, the rst arc optimization is dosed to 1 Gray. The

second arc is then optimized to the existing single arc plan, with the smoothing and lling of cold

spots and the cooling of hot spots, leading to a more homogenous PTV dosing. With the latestsoftware versions, the planner denes two arcs with starting and stopping positions, and then

the optimization occurs to the full 2Gy to the PTV.

The VMAT optimization is a two-step process. A set of ideal intensity maps is generated rst

this takes 10-20 minutes. A leaf sequencing process where leaves move smoothly between

adjacent arc segments follows this. This process used to take 20 minutes but has now been

substantially shortened by employing four quad processors to optimize four arc segments

simultaneously (ref 14).

Additional boost volumes can be added with a second or third arc allowing concomitant boosts

or eld in eld effects. The additional arc may also provide supplementary aperture shapevariation for a complex dose distribution (ref 19). This is particularly useful in head and neck

treatments with primary and nodal PTV, or for boosting a high-risk area within a PTV with a

differential dose; and still adhering to theoretical constraints on overall treatment time.

Picture 3:Axial view of Multiple arc VMAT treatment in a patient with a metallic hip

replacement - showing an exclusion arc segment avoiding entry dose through the

prosthesis (Picture source Premion).


13/36



11

VMAT TREATMENT DELIVERY TIMES

At the commencement of treatment the gantry is at 178 degrees, and then travels in ananticlockwise direction (by convention) nishing at gantry position 182 degrees. As described

by Ling (ref 11) the current mechanical constraints imposed by the maximum MLC leaf speed

is 5mm per degree, corresponding to about 2.5cm per second. The allowable dose rate

modulation is 30-600 monitor units per minute. When more than 2MU per degree is needed at

certain beam angles, the gantry will decelerate to allow delivery of more radiation dose.

This full rotation takes approximately 85 seconds. In a double arc treatment the second arc is

typically slightly shorter in duration as there is somewhat less modulation and the combined

treatment takes 155-170 seconds, with less than 5 seconds needed between arcs for the

collimator to rotate 5 degrees to the new start position. The second arc is given in a clockwise

direction starting with the gantry at 182 degrees and nishing at the original start location of

178 degrees.

Note in Figure 4 how more MU are delivered in the lateral portals where the gantry rotation

slows down. OAR constraints on the bladder and rectum limit dose delivery anteriorly and

posteriorly.

Also note that in the single arc plan there is asymmetry in that in this case more MU are given

in the second half of the rotation than the rst half. This asymmetric bias is a feature of the

planning system and one of the major factors in the move to double arc treatments where the

rotational bias is corrected by re-optimization, with gantry rotation in the opposite direction.

Figure 4:Diagram showing variation in dose delivery during a single gantry rotation in a VMAT prostate plan.

(Picture courtesy Yves Archambauld)


14/36



RADIOBIOLOGICAL CONSIDERATIONS

The absolute reduction in treatment delivery time achieved by single or double arc VMAT

compared to a seven-eld sliding window IMRT in the Amsterdam paper ranged between 6 and

11 minutes (ref 6). This reduction in treatment time may increase the effectiveness of a given

dose by up to 20%, depending on the tumour type (ref 8).

HEAD AND NECK TREATMENTS

After Vancouver - where Otto developed his VMAT algorithm-one of the rst centres in the world

to have access to VMAT was the VU University Medical Centre, Amsterdam, where there is

a very strong medical physics research department. The VUMC has research collaborations

with Varian Medical Systems. Head and neck treatments require multiple avoidance volumes

of normal tissues to be spared including the parotid glands and the spinal cord. The clinical

benets of sparing the parotid glands, with resulting reduction in xerostomia, is a major benet

for IMRT compared to conventional 3D conformal radiotherapy (ref 5). For head and neck

treatments, IMRT uses a larger number of static beams and monitor units, which typically leads

to treatment times of 20 minutes and more patient exposure to scattered low-dose irradiation.

The increase in the number of IMRT beams increases the degrees of freedom, making

volumetric modulated arc therapy a logical next step in head and neck treatments. CT scans

of 12 patients who had completed IMRT for advanced tumours of the naso-, oro- and hypo-

pharynx were replanned using VMAT with one or two arcs. Calculated doses to the planning

target volume (PTV) and organs at risk (OAR) were compared between IMRT and VMAT plans

(ref 6). The results of this study were startling. The VMAT plans allowed for a mean reduction

in number of monitor units (MU) by nearly 60%, relative to seven-eld sliding-window IMRT

plans. Dose to healthy organs not in the proximity of the PTV arises largely from collimator

transmission and scatter dose from the linac, and this dose is proportional to the MU. Such

scattered doses can increase the risk of secondary tumours (ref 7). These chances are now

reduced by the use of VMAT without concessions to the dose distributions.

The VMAT plans achieved a similar sparing of all OAR as IMRT. Double arc VMAT provided the

best dose homogeneity to PTV with a lower standard deviation of PTV dose (1.4Gy) compared

to single arc (2.0Gy) and IMRT (1.7Gy).

The conclusion of this important study was that VMAT was a fast, safe and accurate technique

that uses fewer monitor units than conventional head and neck IMRT. Because the delivery

of VMAT was fast and allowed for large reductions in MU, VMAT had replaced IMRT for all

indications at VUMC Amsterdam by November 2008. Double arc plans provided at least similar

sparing of OAR and better dose homogeneity than single arc or IMRT.

The rst VMAT head and neck treatments in Australia were planned and carried out in June2010, using a double arc technique (ref 13).

PROSTATE

In describing the initial clinical experience of VMAT at the University of Alabama at Birmingham

(ref 17), an early adopting centre that started in May 2008, 33 patients with prostate cancer

were treated in the rst 12 months to April 2009. Of these, 16 were prostate only, 5 were

prostate + seminal vesicles and 12 were prostate + SV + pelvic nodes. When compared with

7 eld IMRT comparison plans, the mean delivery time difference was 2 min for the prostate

only volumes and 6 min for the prostate + SV + nodes volumes favouring VMAT, even though

the double arc technique was preferred for the composite volume plans over a single arc. Theauthors concluded that VMAT was a valuable clinical tool that was able to efciently able to

deliver radiotherapy in 1.5-3 minutes (single or double arcs) (ref 17).


15/36



13

The rst VMAT prostate treatments in Australia were planned and carried out in March 2009.

More centres in Queensland, New South Wales and Victoria have commenced in the last 18

months, with the numbers of patient courses and experience growing. A presentation was given

to the RANZCR meeting in October 2009 showing the dosimetric advantages of the double arc

technique (ref 14).

In a study including 10 high risk prostate cancer patients with seminal vesicle and pelvic

lymph node involvement, from Duke University, plan comparisons with IMRT and VMAT were

performed with all plans using 18MV photons. For the boost plans that included prostate+SV,

dosimetric parameters in double arc plans were comparable to 7 eld IMRT, whereas the single

arc plans were slightly inferior to IMRT. For the more complicated prostate+SV +nodes volumes,

the authors found that 9 eld IMRT spared the bladder rectum and small bowel more than did

VMAT. The delivery efciency, in terms of treatment time, was noticeably improved with VMAT

when the lymph nodes were involved. The authors point out that this improvement certainly

cannot be prioritized over the apparent dosimetric benet (ref 18). The study was unusual in

using 18MV photon planning which is not undertaken by the vast majority of centres using

IMRT or VMAT with more monitor unit redundancy with the higher energy beams as well asmore collimator scatter and with pair production not seen at lower photon energies, and all of

the international focus will continue to be for using 6MV photons.

BREAST

During left breast radiation therapy, a portion of the heart often receives a substantial dose,

especially with the inclusion of the internal mammary nodes (IMN). The most common

radiotherapy techniques used to treat the breast + IMN is a modied wide tangent or a matched

medial electron strip matched to the photon tangents. IMRT techniques have been developed by

many centres and shown to substantially reduce cardiac dose, but such treatments are complex

to plan and treat employing between six and nine coplanar modular elds equally spaced in a180-190 degree arc around the patients left breast and regional nodes.

Picture 5: Coronal cross-sectional view of Multiple arc VMAT treatment targeting prostate

and pelvic lymph nodes with differential target doses in a composite plan (Picture source

Premion).


16/36



In a planning comparison study from Vancouver, 5 patients treated with 9 eld IMRT were

replanned with VMAT (ref 20). For VMAT, a double arc technique using two 190 degree arcs

with 2cm overlapping jaws were required to optimize over the large treatment volumes. The

authors found that the treatment plans generated using VMAT double arc optimization resulted

in PTV homogeneity similar to that of IMRT or modied wide tangents. The average heart

volumes receiving > 30Gy for VMAT, IMRT or modied wide tangents were 2.6% +- 0.7%, 3.5%

+-0.8%, and 16.4% +- 4.3% respectively.

The average mean dose to the contra lateral medial breast was 3.2 +- 0.6Gy for VMAT, 4.3 +-

0.9Gy for IMRT, and 4.4 +- 4.7Gy for modied wide tangents.

The average ipsilateral lung volumes receiving >20Gy were 16.9% +- 1.1% for VMAT, 17.3% +-

0.9% for IMRT, and 37.3 % +- 7.2% for modied wide tangents.

VMAT reduced the number of monitor units by 30% and the treatment time by 55% compared to

IMRT. The authors concluded that double arc VMAT achieved similar PTV coverage and sparing

of organs at risk as 9 eld IMRT, with fewer monitor units and in a signicantly shorter treatment

time (ref 20).

LUNG

Hypo fractionated stereotactic body radiotherapy (SBRT) for stage 1 non-small cell lung cancer

has been shown to have superior local control compared with conventionally fractionated

radiotherapy (ref 15). In an Amsterdam study, 20 consecutive patients completed VMAT

therapy (ref 16). Two-arc optimization was preferred, with the results of the rst optimized plan

calculated for half of the prescribed dose. This was then used as the base dose for the second

arc optimization, which compensated for any under dosage in the PTV in the base dose plan

arising from lack of electronic equilibrium at lung-tissue interfaces by giving more dose to these

areas. Depending on the fraction size, each SBRT fraction used between 2 and six arcs, as

the initial clinical version of VMAT only allowed for a maximum 999 monitor units per arc. In thechest, tumours situated close to critical normal tissues in the mediastinum, or in close proximity

to the chest wall, required the most modulated plans.

The lung cancer PTV took into account target motion due to respiration, with the VMAT delivery

having important practical advantages in delivery over xed gantry sliding window IMRT,

where the direction of the sliding window over time is in one direction and the leaf motion is

constantly perpendicular or parallel to the tumour motion due to the collimator xed at 0 or 90

degrees. This can lead to a greater than 10% dose discrepancy in IMRT delivery. In contrast,

VMAT delivers VMAT dose to the whole volume continuously during gantry rotation by use of a

collimator angle between 40 and 45 degrees. In addition, the MLC leaves in VMAT plans move

in both directions, and not only one way as in sliding window IMRT.

Conformal and VMAT techniques Lung SBRT had similar dosimetric quality, but VMAT

had improved target coverage and took 59% less time to deliver, although monitor units

were increased by 5%. For lung, multiple partial arc treatments produced high quality hypo

fractionated plans that could be delivered quickly and spared entrance dose from the opposite

lung. For a left sided lung lesion the rst anti-clockwise arc would be stopped at a gantry

angle of approximately 330 degrees, before a second arc rotated clockwise back to the starting

position.


17/36



15

BRAIN

Frameless single shot and fractionated stereotactic radiotherapy and intra-cranial image-guided

radiation therapy and intensity modulated radiation therapy for complex shaped base of skull

tumours with surrounding organs at risk are major skill sets at leading Australian radiation

oncology centres. Carbon bre customized head and neck immobilization shells are required

to be purchased, as part of the rotational arc traverses through the base plate. This has been

commissioned and entered clinical practice at a number of centres in 2010, after a series of plan

comparisons with conventional four and ve eld conformal plans have been undertaken.

The published literature at this time for VMAT intra-cranial treatments is limited. The lack of

current publications under-estimates the high level of interest from clinicians and physicists with

stereotactic planning skills. With the updated software version of VMAT (Eclipse version 8.6) as

well as partial arcs, arcs at variable couch angles can be modeled and planned, and it was this

development that led to the implementation of Australian clinical practice. In particular, the use

of a vertex partial arc with the couch at 90 degrees is a major dosimetric advance available in

VMAT treatments, with starting and stopping angles avoiding eyes and brainstem structures.

This is probably the clinical application showing most clearly the demonstrable superiority of

multiple arcs over single arc VMAT treatments.

In a recently published study of 12 patients delivering frameless stereotactic radiotherapy(SRT) using VMAT, dosimetric indices for conformality, homogeneity and dose gradient

were calculated and compared with published results from other frameless, intracranial SRT

techniques, including CyberKnife, Tomotherapy and static beam IMRT. The results showed that

dose indices compared favourably with other techniques. Median treatment times with double

arc VMAT were 4.8 +/- 1.7 minutes (ref. 25).

Picture 6: Diagram of an Intracranial VMAT beam arrangement using a double-arc technique

combining an axial single arc and a non co-planar partial arc. (Picture source: Premion)


18/36



OTHER CLINICAL APPLICATIONS

In a paper showing the potential benet of VMAT compared with conformal and IMRT

techniques in paediatric cancer, bone marrow sparing whole-abdominopelvic irradiation and,

Matuszak et al., when examining the potential benet of VMAT compared with conventional

techniques in paediatric cancer, whole-abdomino-pelvic techniques and stereotactic body

radiation therapy (SBRT) of the lung and spine found that VMAT reduced the treatment time

of spine SBRT by 37% and improved dose conformality. In more complicated spine cases,the authors found that multiple arc treatments could improve the dose distribution without a

signicant increase in time or MU (ref 12).

In a complex paediatric pelvic case, VMAT reduced the treatment time by 78% and monitor units

by 25% compared to IMRT.

A double isocentre VMAT technique for whole abdominopelvic irradiation was shown to spare

bone marrow whilst maintaining good treatment delivery.

This paper (ref 12) used Pinnacle 3 (cubed) treatment planning system from Phillips (Phillips

Healthcare, Andover, MA, USA), the VMAT module of which was not at that stage interactive

with the MOSAIC linac verication and recording system. The benets were thus theoretical,

but show that other vendors are close behind Varian and Elekta with approved VMAT platforms

for clinical treatment.

QUALITY ASSURANCE

For VMAT commissioning and QA, the two elements to be considered are linac commissioning

and patient specic dosimetry. VMAT treatments are a development from IMRT using static

elds, and institutions implementing VMAT should be familiar with IMRT commissioning and

QA. Standard commissioning includes testing gantry and MLC isocentricity, gantry position

indicators, and dose calibration in both static gantry and arc therapy mode. Picket fence testsat multiple gantry angles are also preformed. This establishes the accuracy of dynamic MLC

position, and dose-rate.

Patient specic dosimetry QA includes the use of phantom dosimetric tests of central isodose

using mini-ion chambers and planar dose distributions using calibrated matrix dosimetry devices

such as those used in IMRT QA of clinical treatment plans. This is undertaken for all patients

(ref 11).

COMPARISON OF HELICAL TOMOTHERAPY AND VMAT TECHNIQUES

A collaborative dosimetric comparison between HT and single arc VMAT was undertaken in

16 cases. Four cancer sites including brain, head and neck, lung and prostate were selected.

Planners were blinded to the plan comparison.

For all the 16 cases compared, the average beam on time was 1.4 minutes for VMAT, and 4.8

minutes for Tomotherapy. The total monitor units were lower in VMAT than in Tomotherapy,

whereas Tomotherapy delivered better target dose homogeneity (7.6% for VMAT and 4.2% for

Tomotherapy). Dose conformation numbers were comparable, with VMAT being superior to

Tomotherapy (0.67 vs. 0.60).

When the initial blinding was taken away and an opportunity given to re-plan the differences

between the two planning techniques in terms of target conformality and avoidance structures

narrowed considerably. A comparison with a double arc VMAT technique was not performed inthis study, but this could have been expected to further improve the plan dose conformality

(ref 24).


19/36



17

Helical Tomotherapy is by denition a multiple rotational therapy, with a body of published

literature conrming it as a treatment delivery system with many of the same dosimetric

advantages that IMRT and VMAT offer, with a unique delivery platform.

CONCLUSIONS

Currently available radiotherapy treatment techniques differ in terms of the trade-offs betweentreatment planning time, treatment delivery time, and overall plan quality. IMRT plan generation

times are shorter than for VMAT plans. (ref 21) Faster processor speeds and use of 4 quad

processors now in use are speeding up the leaf sequencing optimization component of the

VMAT planning.

VMAT either single arc or double arc has signicantly faster treatment delivery times than

IMRT. This may have radiobiological advantages in head and neck cancers where the dose rate

effect of the 2Gy fraction delivery time may be of clinical relevance, and may be have geometric

certainty advantages in targets where intra-fraction organ movement (prostate and lung) is

relevant.

With respect to plan quality, for simple planning target volumes such as prostate alone, a singlearc plan may be acceptable in terms of target coverage and sparing of organs at risk, but

sparing of OAR and PTV dose homogeneity can be further improved by adding a second arc

and repeating the optimization. For more complex volumes, as shown by multiple authors sited

in this document looking at multiple treatment sites in the body, the second arc and optimization

is not optional, and the additional arc degrees of modulation are required for optimal plan

delivery such that a single arc plan would be an unacceptable compromise.

At the ASTRO meeting held in San Diego in November 2010, more than twenty abstracts

describing VMAT in multiple clinical settings were presented, with an emerging consensus of

its utility and adaptability for state-of-the-art radiotherapy treatment delivery at multiple leading

centres around the world.

Specically, this document provides signicant evidence that volumetric modulated arc

therapy, when performed with multiple arcs, achieves superior target dose homogeneity

and adjacent normal tissue sparing in a range of tumour sites when compared to 6 eld 3D

conformal radiotherapy. It is in all ways equivalent to the best planned multiple eld IMRT in

dosimetric terms and is considerably more efcient in terms of treatment delivery, with important

radiobiological advantages to the patient, who also benets from reduced discomfort associated

with a reduction in treatment times, particularly for complex volumes such as head and neck

sites.


20/36



BIBLIOGRAPHY APPENDIX I

1. Ling CC, Burman C, Chui CS et al. Conformal radiation treatment of prostate cancer using

inversely-planned intensity modulated photon beams produced with dynamic multileaf

collimation. Int J Radiat Oncol Biol Phys 1996, 35(4): 721-30

2. Veldeman L, Madani I, Hulstsert F, et al. Evidence behind use of intensity-modulatedradiotherapy: a systemic review of comparative clinical studies. Lancet Oncology 2008,9(4):

367-375

3. Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys. 2008; 35(1):

310-317

4. Elekta Inc. VMAT Technology review 2009http://www.elekta.com/healthcare_international_

elekta_vmat.php

5. Pow EH, Kwong DL McMillan AS et al. Xerostomia and quality of life after intensity-modulated

radiation therapy vs. conventional radiotherapy for early stage nasopharyngeal carcinoma:

Initial report on a randomized controlled trial. Int J Radiat Oncol Biol Phys 2006; 66: 981-991

6. Verbakel W, Cuupers J, Hoffmans D et al Volumetric Intensity Modulated Arc Therapy vs.

Conventional IMRT in Head and Neck Cancer: A Comparative Planning and Dosimetric Study.

Int J Radiat Oncol Biol Phys 2009, 74(1): 252-259

7. Hall EJ Intensity-modulated radiation therapy, protons, and the risk of second cancers. Int J

Radiat Oncol Biol Phys 2006; 65(1): 1-7

8. Bewes JM et al. The radiobiological effect of intra-fraction dose-rate modulation in intensity

modulated radiation therapy (IMRT) Phys Med Biol 53: 3567

9. Borteld and Webb. Single Arc IMRT? 2009 Phys Med Biol, 2009; 54: N9-20

10. Verbakel et al. Comments on Single Arc IMRT? Phys Med Biol, 2009; 54: L31-34

11. Ling CC, Zhang P, Archambauld Y. Commissioning and quality assurance of RapidArc

radiotherapy delivery system. Int J Radiat Oncol Biol Phys 2008; 72:575-581

12. Matuszak MM, Yan D, Grills I, and Martinez A. Clinical Applications of Volumetric Modulated

Arc Therapy. Int J Radiat Oncol Biol Phys 2010; 77(2): 608-616

13. Dr Tom Eade, RNSH, personal communication

14. MacKean J, Buchanan M, Kenny J Murray M. Initial experience with volumetric modulated arc

therapy one revolution or two. Presented at RANZCR meeting Oct 2009.

15. Grutters JP et al Comparison of the effectiveness of radiotherapy with photons, protons and

carbon ions fore non small cell lung cancer: A meta-analysis. Radiother Oncol 2010; 95:32-40

16. Ong CL, Verbakel W et al. Dosimetric Impact of Interplay effect on RapidArc lung stereotactic

lung delivery. Int J Radiat Oncol Biol Phys. 2010 Article in press Oct 1.

17. Pople RA, et al. RapidArc radiation therapy: rst year experience at the University of Alabama

at Birmingham. Int J Radiat Oncol Biol Phys 2010; 77(3): 932-941

18. Yoo S, Wu J, Lee R, Yin FF Radiotherapy Treatment plans with RapidArc for Prostate Cancer

involving Seminal Vesicles and Lymph Nodes. Int J Radiat Oncol Biol Phys 2010; 76 (3): 935-942


21/36



19

19. Tang G, Earl MA, Yu CX et al. Comparing radiation treatments using intensity modulated

beams, multiple arcs and single arcs. Int J Radiat Oncol Biol Phys 2010; 76(5): 1554-1562

20. Popes CC, Olivotto IA, Beckham WA et al. Volumetric Modulated Arc therapy improves

dosimetry and reduces treatment time compared to conventional intensity modulated

radiotherapy for locoregional radiotherapy of left sided breast cancer and internal mammary

nodes. Int J Radiat Oncol Biol Phys 2010; 76 (1): 287-295

21. Oliver et al. Trade-offs in IMRT, RapidArc and Tomotherapy. Journal of App Clin Med Phys.

2009; 10(4): 117-131

22. Mackie TR. History of Tomotherapy. Phys Med Biol. 2006; 51 : R427-453

23. Mackie TR, Balog J, Ruchala K et al. Tomotherapy. Semin Radiat Oncol. 1999; 9 : 108-117

24. Rong Y, Tang G, Welsh JS et al, Helical Tomotherapy versus Single-Arc Intensity Modulated

Arc Therapy: A Collaborative Dosimetric comparison between two institutions. Int J Radiat

Oncol Biol Phys article in press Jan 14 2011

25. Mayo CS, Ding L, Addesa A et al, Initial experience with Volumetric IMRT (RapidArc) for

Intracranial Stereotactic Radiosurgery. Int J Radiat Oncol Biol Phys 2010; 78 (5): 1457-1466


22/36



APPENDIX II: DETAILED EVIDENCE FOR THE BENEFITS OF SINGLE

AND MULTI ARC VMAT

Ref SiteNo. of

Patients

No. of

ArcsConclusion

(1) H&N 4 1/2 IMRT and dual arc VMAT achieved a similar plan quality,

while single arc could notprovide an acceptable plan quality.

Dual arc VMAT delivery time is about 30%of IMRT delivery

time. Dual arc VMAT is a fast and accurate technique for the

treatment of head and neck cancer. It applies similar number

of MUs as IMRT, but the treatment time is strongly reduced,

maintaining similar or better dose conformity to the PTV and

OAR sparing.

(2) H&N 25 1 Equivalent or superior target coverage and sparing of OARs

were achieved with VMAT compared to IMRT. CI(95%) of the

elective PTV was improved from 1.7 with IMRT to 1.6 with

VMAT. VMAT reduced the number of MUs by 8.5% to 460+/-63MUs per fraction. The treatment time was on average reduced

by 35%.

(3) Abdominal

Nodes

14 1 Rapid Arc improved PTV coverage (V(95%) = 90.2% +/- 5.2%

for RA compared with 82.5% +/- 9.6% and 84.5% +/- 8.2%

for Conformal RT and IMRT, respectively). Most planning

objectives for organs at risk were met by all techniques except

for the duodenum, small bowel, and stomach, in which the

CRT plans exceededthe dose/volume constraints in some

patients. The MU/fraction values were as follows: 2186 +/- 211

for RA, 2583 +/- 699 for IM, and 1554 +/- 153 for CRT. Effective

treatment time resulted as follows: 3.7 +/- 0.4 min for RA, 10.6

+/- 1.2 min for IM, and 6.3 +/- 0.5 min for CRT. Delivery ofSBRT by RA showed improvements in conformal avoidance

with respect to standard conformal irradiation. Delivery

parameters conrmed logistical advantages of Rapid Arc,

particularly compared with IMRT.

(4) Pelvis N/S 1 Dose-volume histogram comparisons demonstrate that this

VMAT planning method offers multiple dose level target

coverage comparable to that from a standard IMRT approach.

The VMAT plans also show superiorsparing of critical

structures such as the rectum and bladder. Delivery times are

reduced with the VMAT method, and the results of dosimetric

verication, resilience and repeatability tests indicate that the

solution is robust.

(5) CNS H&N

Lung

Prostate

6 1-3 For OAR sparing, the non-coplanar plans showed signicant

improvement for the cases with intra-cranial targets.

For example, the maximum and mean doses to brainstem were

reduced by 23% and 34%reduction. The average maximum

dose to the chiasm was also reduced by 61%. For extra-cranial

cases, however, there are no consistent improvements in OAR

sparing for the non-coplanar plans. The average treatment

delivery time increased from 1.9 to 4.5 minutes for the non-

coplanar plans. For extra-cranial cases, only modest gains in

OAR sparing were observed particularly for structures that are

in close proximity to the targets.


23/36



21

Ref SiteNo. of

Patients

No. of

ArcsConclusion

(6) Brain Mets 1 1-3 Multiple noncoplanar arcs showed small improvements in

the conformity indexes compared with the single-arc/single-

isocenter and triple-arc (coplanar)/triple-isocenter plans.

Multiple arc plans (triple-arc (noncoplanar)/single-isocenter

and triple-arc (coplanar)/triple-isocenter) showed smaller 12-Gy isodose volumes in scenarios involving three metastases

spaced closely together, with only small differences noted

among all plans involving lesions spaced further apart. Initial

results suggest that single-isocenter VMAT plans can be used

to deliver conformity equivalent to that of multiple isocenter

VMAT techniques. For targets that are closely spaced, multiple

noncoplanar single-isocenter arcs might be required. VMAT

radiosurgery for multiple targets using a single isocenter can be

efciently delivered, requiring less than one-half the beam time

required for multiple isocenter set ups. VMAT radiosurgery will

likely replace multi-isocenter techniques for linear accelerator-

based treatment of multiple targets.

(7) Cervix 8 1 VMAT had an improved homogeneity (D(5%)-D(95%) = 3.5 +/-

0.6 Gy for VMAT and 4.3 +/- 0.8 Gy for IMRT) and conformity

index (CI(90%) = 1.30 +/- 0.06 for VMAT and 1.41 +/- 0.15 for

IMRT). Rectal mean dose was reduced by about 6 Gy. For the

bladder, VMAT allowed a reduction of mean dose ranging from

approximately 4 to 6Gy. Similar trends but with smaller absolute

differences were observed for the small bowel and left and right

femur. NTCPcalculations on bladder and rectum conrmed

the DVH data with a potential relative reduction ranging

from 30 to 70%from IMRT to VMAT. The healthy tissue was

signicantly less irradiated in the medium to high dose regions

(from 20 to 30 Gy) and the integral dose reductionwith VMAT

was about 12%compared to IMRT. VMAT shows signicant

improvements in organs at risk and healthy tissue sparing with

uncompromised target coverage leading to better conformal

avoidance of treatments w.r.t. conventional IMRT.

(8) Various N/S 1-2 For prostate cancer and vertebral metastases single arc VMAT

led to similar plan quality as compared to IMRT. For treatment

of the hypopharynx/larynx cancer, a second arc was necessary

to achieve sufcient plan quality. Treatment time was reduced in

all cases to 35% to 43%as compared to IMRT. Times required

for optimization and dose calculation, however, increased

by a factor of 5.0 to 6.8. Similar or improved plan quality can

be achieved with VMAT as compared to IMRT at reducedtreatment times but increased calculation times.

(9) Breast 7 difcult

anatomy

1-2 One P-Arc was to be on average a better technique, as it

provides a PTV dose distribution highly conformal (Conformity

index 1.45), homogeneous (D(5%)-D(95%)=15.6%), with

adequate coverage (V(90%)=96.4%) and a limited involvement

of the ipsilateral lung (MLD approximately 9 Gy, V(5 Gy)

approximately 36%, NTCP


24/36



Ref SiteNo. of

Patients

No. of

ArcsConclusion

(10) Prostate

H&N

20 1-3 Single arc VMAT improved target coverage and dose

homogeneity in radiotherapy for prostate cancer. Two and

three VMAT arcs were required to achieve equivalent results

compared to IMRT in postoperative and primary radiotherapy

for pharyngeal cancer, respectively. In radiotherapy for cancerof the paranasal sinuses, multiarc VMAT resulted in increased

spread of low doses to the lenses and decreased target

coverage in the region between the orbits. The complexity of

the target volume determined whether single arc VMAT was

equivalent to IMRT. Multiple arc VMAT improved results

compared to single arc VMATat cost of increased delivery

times, increased monitor unites and increased spread of low

doses.

(11) Prostate 10 1 VMAT plans resulted in a statistically signicant reduction in

the rectal V25Gy parameter of 8.2%on average over the IMRT

plans and lower rectal NTCP. 18.6%fewer monitor units and a

delivery time reduction of up to 69%.VMAT plans resulted inreductions in rectal doses for all 10 patients in the study. Given

the target coverage was equivalent, the VMAT plans were

superior.

(12) Prostate 10 1 VMAT provided satisfactory target conformality and OAR

sparing comparable to IMRT. VMAT required fewer MU than

IMRT (relative reduction of 19%;p= 0.006). Mean treatment

time was 133 seconds for VMAT, versus 358 seconds for

IMRT (p= 0.006). Grade 3 or worse acute toxicities were not

seen.

(13) Review

Article

N/A N/A VMAT tends to yield similar dose distribution to MRT with

xed gantry. VMAT also decreases monitor units as well astreatment delivery time to less than 5 minutes.However,

VMAT is an IMRT technique more difcult to master than S&S

IMRT technique because there are more variable parameters.

(14) Review

Article

N/A N/A Arc IMRT appears a new promising IMRT modality, decreasing

dramatically treatment duration. However, this IMRT-based

dosimetric benet may not be translated into a full clinical

benet, if intra-pelvic prostate motion is not taken in account.

Image-guided radiotherapy (IGRT) should be therefore

associated with IMRT for a maximal clinical benet. This article

is a literature review showing the interest of both combined

approaches.


25/36



23

Ref SiteNo. of

Patients

No. of

ArcsConclusion

(15) Brain Mets 10 1-2 Compared with IMRT, the maximum dose in Rapid Arc 2 plans

to the brainstem, left and right optic nerves, left and right

lens was reduced by 1.6 Gy, 6 Gy, 3 Gy, 1.5 Gy, 1.3 Gy,

respectively. The percentage of healthy tissue volume receiving

5 Gy was larger with RA1 (56.7%) and RA2 (57.1%) than withIMRT (52.9%), while the percentages of volume receiving 15

Gy and 20 Gy were smaller with RA1 (27.1%, 18.7%) and RA2

(25%, 16.3%) than with IMRT (28.8%, 19.1%). No signicant

difference was observed between RA1 and RA2. The mean

number of MU per fraction of 5 Gy was 1944 +/- 374 (IMRT),

1199 +/- 173 (RA1) and 1387 +/- 186 (RA2), respectively.

Compared with IMRT, the MUs were reduced by 36.8% and

27.2% with RA1 and RA2. The pure beam-on time needed per

fraction was 6.5 +/- 1.2 min (IMRT), 1.25 min (RA1) and 2.5

min (RA2),respectively. The beam-on time for RA1 and RA2

was approximately 80% and 40% lesscompared to IMRT.

2 Arcs achieves slight improvements in PTV coverage and

sparing of organs at risk. The treatment efciency, using less

monitor unitsand shorter treatment delivery time, is the

most obvious advantage.

(16) Various 4 1-2 Volumetric modulated arc therapy reduced the treatment time

of spine SBRT by 37% and improved isodose conformality.

Conformal and VMAT techniques for lung SBRT had similar

dosimetric quality, but VMAT had improved target coverage

and took 59% less time to deliver, although monitor units

were increased by 5%. In a complex pediatric pelvic example,

VMAT reduced treatment time by 78% and monitor units by

25% compared with IMRT. A double-isocenter VMAT technique

for WAPI can spare bone marrow while maintaining good

delivery efciency.

(17) Lung 21 1 Lung V(20/12.5/10/5) were less with VMAT (relative reduction

4.5%,p = .02; 3.2%, p = .01; 2.6%, p = .01; 4.2%, p = .03,

respectively). Mean/maximum-doses to PTV, dose to additional

OARs, 95% isodose line conformity, and target volume

homogeneity were equivalent. VMAT improved conformity

at both the 80% (1.87 vs. 1.93, p = .08) and 50% isodose

lines (5.19 vs. 5.65, p = .01). Treatment times were reduced

signicantly with VMAT (mean 6.1 vs. 11.9 min, p < .01) Single

arc VMAT planning achieves highly conformal dose distributions

while controlling dose to critical structures, including signicant

reduction in lung dose volume parameters. Employing a VMATtechnique decreases treatment times by 37-63%, reducing the

chance of error introduced by intrafraction variation. The quality

and efciency of VMAT is ideally suited for stereotactic lung

radiotherapy delivery.


26/36



Ref SiteNo. of

Patients

No. of

ArcsConclusion

(18) Prostate

H&N

10 1 The VMAT optimization problem is formulated as a large-scale

convex programming problem solved by a column generation

approach. The algorithm was preliminarily tested on ve

prostate and ve head-and-neck clinical cases, each with one

full gantry rotation without any couch/collimator rotations. Highquality VMAT plans have been generated for all ten cases

with extremely high efciency. It takes only 5-8 min on CPU

(MATLAB code on an Intel Xeon 2.27 GHz CPU) and 18-31 s

on GPU (CUDA code on an NVIDIA Tesla C1060 GPU card) to

generate such plans. The authors have developed an aperture-

based VMAT optimization algorithm which can generate

clinically deliverable high quality treatment plans at very high

efciency.

(19) Lung 18 1 VMAT SBRT plans achieved a superior conformity index (CI)

and lower V(45 Gy)to chest wall (p


27/36



25

Ref SiteNo. of

Patients

No. of

ArcsConclusion

(24) Prostate 24 1 Treatment delivery times were 1.5-2 minutes for the VMAT

plans vs. 7-9 minutes for the xed eld IMRT plans.

VMAT plans that are equivalent to or superior to xed eld

IMRT plans can be achieved for most patients with

localized prostate cancer. VMAT plans offer the potential forreduced doses to adjacent organs, especially at lower dose

levels (V40). VMAT plans can be delivered signicantly faster

than xed eld IMRT plans, allowing potential for operational

efciency and improved patient comfort.

(25) H&N 45 N/S Only 28% of patients experienced G3 mucositis, 14% G3

dermitis 44% had G2 dysphagia. Nobody required feeding

tubes to be placed during treatment. These preliminary

results stated that volumetric modulated arc therapy in locally

advanced head and neck cancers is feasible and effective, with

acceptable

(26) Prostate 10 N/S VMAT and cIMRT boosted an average of 68.8 and 63.5% of the

CTV to >or=120% of the prescription dose (P=0.002). All dose

constraints were kept within predened limits. VMAT and cIMRT

required an average of 949 and 1819 monitor units and 3.7 and

9.6min, respectively, to deliver a single radiation fraction.VMAT

is able to boost more of the CTV to >or=120% than cIMRT

without contravening OAR dose constraints, and uses 48%

fewer monitor units. Treatment times were 61%less than with

cIMRT.

(27) CNS 10 N/S There was equivalent PTV coverage, homogeneity, and

conformality. VMAT signicantly reduced maximum and mean

retinal, lens, and contralateral optic nerve doses compared with

IMRT (p < 0.05). Brainstem, chiasm, and ipsilateral optic nervedoses were similar. For 2-Gy fractions, mean monitor units

were as follows: cIMRT = 789 +/- 112 and VMAT = 363 +/- 45

(relative reduction 54%, p = 0.002), and mean treatment times

(min) were as follows: cIMRT = 5.1 +/- 0.4 and VMAT = 1.8 +/-

0.1 (relative reduction 65%, p = 0.002). VMAT achieved equal

or better PTV coverage and OAR sparing while using fewer

monitor units and less time to treat high-grade gliomas.

(28) Various 12 N/S Multiarc (IMAT) provided the best plan quality, while single-

arc VMAT achieved dose distributions comparable to those of

IMRT, especially in the complicated head-and-neck and brain

cases. Both VMAT and IMAT showed effective normal tissue

sparing without compromising target coverage and delivereda lower total dose to the surrounding normal tissues in some

cases. IMAT provides the most uniform and conformal dose

distributions, especially for the cases with large and complex

targets, but with a delivery time similar to that of IMRT; whereas

VMAT achieves results comparable to IMRT with signicantly

faster treatment delivery.

(29) CNS 3 N/S For the smallest tumor (26.7 cc), multiple-arc RA showed

advantages over IMRT and HT in PTV coverage, dose

homogeneity, and OAR sparing. For the larger brain tumors

both HT and RA-NCPA offered high quality of PTV coverage

and dose homogeneity.


28/36



Ref SiteNo. of

Patients

No. of

ArcsConclusion

(30) Prostate 12 HT provided superior conformity and signicantly less rectal

volume exposed to 65 Gy and 40 Gy, as well as EUD/NTCP

of rectum than step-and-shoot IMRT, whereas VMAT had a

slight dosimetric advantage over step-and-shoot IMRT. Notably,

signicantly lower MUswere needed for VMAT (309.7 +/-35.4) and step-and-shoot IMRT (336.1 +/- 16.8) than for HT

(3368 +/- 638.7) (p < 0.001). The treatment time (minutes)

was signicantly shorterfor VMAT (2.6 +/- 0.5) than step-

and-shoot IMRT (3.8 +/- 0.3) and HT (3.8 +/- 0.6) (p < 0.001).

VMAT and step-and-shoot IMRT have comparable dosimetry,

but treatment efciency is signicantly higher for VMAT than for

step-and-shoot IMRT and HT.

(31) H&N 12 1-2 RA plans allowed for a mean reduction in number of monitor

units (MU) by nearly 60%,relative to seven eld sliding window

IMRT plans. RA plans achieved similar sparing of all OAR as

IMRT. Double arc RA provided the best dose homogeneity

to PTV with a lower standard deviation of PTV dose (1.4Gy), vs. single arc plans (2.0 Gy) and IMRT (1.7 Gy). Film

measurements showed good correspondence with calculated

doses; the mean gamma value was 0.30 (double arc) and

area of the lm with a gamma exceeding 1 was 0.82%.RA is a

fast, safe, and accurate technique that uses lower MUs than

conventional IMRT. Double arc plans provided at least similar

sparing of OAR and better PTV dose homogeneity than

single arc or IMRT.

(32) Anal 10 1-2 Both IMRT and RA2 resulted in superior coverage of PTV than

RA1 that was slightly inferior for conformity and homogeneity (p

< 0.05).Conformity index (CI95%) for the PTV2 was 1.15 0.15

(RA2), 1.28 0.22 (IMRT), and 1.79 0.5 (RA1). Homogeneity(D5% - D95%) for PTV2 was 3.21 1.16 Gy (RA2), 2.98

0.7 Gy (IMRT), and 4.3 1.3 Gy (RA1). VMAT showed to be

superior to IMRT in terms of organ at risk sparing. For bowel,

the mean dose was reduced by 4 Gy by RA2compared

to IMRT. Similar trends were observed for bladder, femoral

heads, and genitalia. The DVH of iliac crests and healthy

tissue resulted in comparable sparing for the low doses (V10

and V20). Compared to IMRT, mean MUsfor each fraction

was signicantly reducedwith VMAT (p = 0.0002) and the

treatment time was reduced by a 6-fold extent. VMAT with 2

arcs was able to deliver equivalent treatment plan to IMRT

in terms of PTV coverage. It provided a better organ at risksparing and signicant reductions of MU and treatment time per

fraction.


29/36



27

Ref SiteNo. of

Patients

No. of

ArcsConclusion

(33) Review N/S N/S Intensity modulated radiation therapy (IMRT) offers optimal

dosimetric and clinical results in terms of acute toxicity, allows

augmenting the dose to the target volumes and therefore,

appears promising for local control and disease-free survival.

However, several pitfalls to this treatment are to be considered,namely a long treatment time and a high number of monitor

unit (MU) required. The dosimetric results of the volumetric

modulated arctherapy gives at least similar target coverage and

preservation of organs at risk, while signicantly reducing the

number of required MUs and the overall treatment time. This

has a potential impact on the treatment quality and the potential

risk of secondary cancers. Volumetric modulated arctherapy

allows implementation of stereotactic radiation therapy and

complex treatments previously considered not feasible with

IMRT. The future will involve this technology of high precision

to determine the dose and to the target in real time using the

image-guided radiotherapy. Tools combining these two methods

are in development.

(34) Prostate 9 1-2 RESULTS: For MIMiC/IMRT(MLC)/VMAT2x/VMAT1x/3D-

CRT, mean CI was 1.5/1.23/1.45/1.51/1.46 and HI was

1.19/1.1/1.09/1.11/1.04. For a prescribed dose of 76 Gy,

mean doses to organs-at-risk (OAR) were 50.69 Gy/53.99

Gy/60.29 Gy/61.59 Gy/66.33 Gy for the anterior half of the

rectum and 31.85 Gy/34.89 Gy/38.75 Gy/38.57 Gy/55.43 Gy

for the posterior rectum. Volumes of non-target normal tissue

receiving > or =70% of prescribed dose (53 Gy) were 337

ml/284 ml/482 ml/505 ml/414 ml, for > or =50% (38 Gy) 869

ml/933 ml/1155 ml/1231 ml/1993 ml and for > or =30% (23 Gy)

2819 ml/3414 ml/3340 ml/3438 ml /3061 ml. D(95%) was 69.79

Gy/70.51 Gy/71,7 Gy/71.59 Gy/73.42 Gy. Mean treatment time

was 12 min/6 min/3.7 min/1.8 min/2.5 min. All approaches

yield treatment plans of improved quality when compared to

3D-conformal treatments, with serial tomotherapy providing

best OAR sparing and VMAT being the most efcient treatment

option in our comparison. Plans which were calculated with

3D-CRT provided good target coverage but resulted in higher

dose to the rectum.

(35) Brain Mets 10 N/S RA provides a new alternative for single-fraction SRS irradiation

combining advantages of short treatment time with lower

number of MU and better conformity in addition to accuracy of

stereotactic localisation in selected cases with uncomplicatedclinical realization.


30/36



Ref SiteNo. of

Patients

No. of

ArcsConclusion

(36) Spine 10 1-2 The PTV DVHs were comparable between VMAT and

IMRT plans in the shoulder (D(99%)-D(90%)), slope

(D(90%)-D(10%)), and tail (D(10%)-D(1%)) regions. Only

VMAT(2arc) had a better conformity indexthan IMRT (1.09

vs. 1.15, p = 0.007). For cord sparing, IMRT was the best, andVMAT(1arc) was the worst. Use of IMRT achieved greater than

10% more D(1%) sparing for six of 10 cases and 7% to 15%

more D(10%) sparing over the VAMT(1arc). The differences

between IMRT and VAMT(2arc) were smaller and statistically

nonsignicant at all dose levels. The differences were also

small and statistically nonsignicant for other OAR sparing.

The mean monitor units (MUs) were 8711, 7730, and 6317 for

IMRT, VMAT(1arc), and VMAT(2arc) plans, respectively, with a

26%reduction from IMRT to VMAT(2arc). The mean treatment

time was 15.86, 8.56, and 7.88min for IMRT, VMAT(1arc,) and

VMAT(2arc). The difference in integral dose was statistically

nonsignicant. Although VMAT provided comparable PTV

coverage for spine SBRT, 1arc showed signicantly worse

spinal cord sparing compared with IMRT, whereas 2arc was

comparable to IMRT. Treatment efciency is substantially

improved with the VMAT.

(37) Phantom N/A N/A The study showed not only that SIB by RA can achieve

superior plans compared with SEQ plans on the same platform

and SIB plans on HT, but also the feasibility to optimize

prescription dose in a SIB plan. A maximal therapeutic ratio can

be achieved with BTV dose 50-100% higher than the PTV dose,

depending on the shape and position of the tumor. The results

show that up to 4 arcs may be necessary to provide uniform

dose to the surface of the PTV with the current version of the

PRO.

(38) Prostate 10 1-2 In the primary IMRT with PTV(P), average mean doses to

bladder, rectum and small bowel were lower by 5.9%, 7.7%

and 4.3%, respectively, than in the primary 1ARC and by 3.6%,

4.8% and 3.1%, respectively, than in the primary 2ARC.In

the boost IMRT with PTV(B), average mean doses to bladder

and rectum were lower by 2.6% and 4.8% than with the boost

1ARC and were higher by 0.6% and 0.2% than with the boost

2ARC. Integral doses were 7% to 9% higher with VMAT than

with IMRT for both primary and boost plans. Treatment delivery

time was reducedby 2-7 minutes using VMAT. For PTVs

including prostate, seminal vesicles, and lymph nodes, IMRTperformed better in dose sparing for bladder, rectum, and small

bowel than did VMAT. For PTVs including prostate and seminal

vesicles, VMAT with two arcs provided plans comparable to

those for IMRT. The treatment delivery is more efcient with

VMAT.

(39) Prostate 11 1 Patient-averaged PTV V95, D95, mean dose, and tumor control

probability in VMAT plans were 96%, 82.6 Gy, 88.5 Gy, and

0.920, respectively, vs. 97%, 84.0 Gy, 88.9 Gy, and 0.929 in

IMRT plans. All critical structure dose requirements were met.

The VMAT plans presented better rectal wall sparing, with

a reduction of 1.5%in normal tissue complication probability.

An advantage of VMAT plans was that the average numberof MUs (290 MU) was less than for IMRT plans (642 MU).

The VMAT technique can reduce beam on time by up to 55%

while maintaining dosimetric quality comparable to that of the

standard IMRT approach.


31/36



29

BIBLIOGRAPHY APPENDIX II

(1) J. Staffurth, A review of the clinical evidence for intensity-modulated radiotherapy, Clinical

Oncology (Royal College of Radiologists (Great Britain)), vol. 22, no. 8, pp. 643-657, Oct.

2010.

(2) J. Alvarez-Moret, F. Pohl, O. Koelbl, and B. Dobler, Evaluation of volumetric modulated arctherapy (VMAT) with Oncentra MasterPlan for the treatment of head and neck cancer,

Radiation Oncology (London, England), vol. 5, p. 110, 2010.

(3) A. Bertelsen, C. R. Hansen, J. Johansen, and C. Brink, Single Arc Volumetric Modulated Arc

Therapy of head and neck cancer, Radiotherapy and Oncology: Journal of the European

Society for Therapeutic Radiology and Oncology, vol. 95, no. 2, pp. 142-148, May. 2010.

(4) M. Bignardi et al., Critical appraisal of volumetric modulated arc therapy in stereotactic

body radiation therapy for metastases to abdominal lymph nodes, International Journal of

Radiation Oncology, Biology, Physics, vol. 75, no. 5, pp. 1570-1577, Dec. 2009.

(5) C. J. Boylan, C. Golby, and C. G. Rowbottom, A VMAT planning solution for prostate patients

using a commercial treatment planning system, Physics in Medicine and Biology, vol. 55, no.

14, pp. N395-404, Jul. 2010.

(6) D. Cao et al., Dosimetric Benet of Non-coplanar VMAT Delivery, International Journal of

Radiation Oncology*Biology*Physics, vol. 78, no. 3, p. S823, Nov. 2010.

(7) G. M. Clark, R. A. Popple, P. E. Young, and J. B. Fiveash, Feasibility of single-isocenter

volumetric modulated arc radiosurgery for treatment of multiple brain metastases,

International Journal of Radiation Oncology, Biology, Physics, vol. 76, no. 1, pp. 296-302, Jan.

2010.

(8) L. Cozzi et al., A treatment planning study comparing volumetric arc modulation with

RapidArc and xed eld IMRT for cervix uteri radiotherapy, Radiotherapy and Oncology:

Journal of the European Society for Therapeutic Radiology and Oncology, vol. 89, no. 2, pp.

180-191, Nov. 2008.

(9) B. Dobler, K. Weidner, and O. Koelbl, Application of volumetric modulated arc therapy

(VMAT) in a dual-vendor environment, Radiation Oncology (London, England), vol. 5, p. 95,

2010.

(10) A. Fogliata, A. Clivio, G. Nicolini, E. Vanetti, and L. Cozzi, A treatment planning study

using non-coplanar static elds and coplanar arcs for whole breast radiotherapy of patients

with concave geometry, Radiotherapy and Oncology: Journal of the European Society for

Therapeutic Radiology and Oncology, vol. 85, no. 3, pp. 346-354, Dec. 2007.

(11) M. Guckenberger, A. Richter, T. Krieger, J. Wilbert, K. Baier, and M. Flentje, Is a single arc

sufcient in volumetric-modulated arc therapy (VMAT) for complex-shaped target volumes?,

Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and

Oncology, vol. 93, no. 2, pp. 259-265, Nov. 2009.


32/36



(12) N. Hardcastle, W. A. Tom, K. Foo, A. Miller, M. Carolan, and P. Metcalfe, Comparison of

prostate imrt and vmat biologically optimised treatment plans, Medical Dosimetry: Ofcial

Journal of the American Association of Medical Dosimetrists, Aug. 2010.

(13) K. Ishii et al., Clinical Application of Aperture-based VMAT with Ring-shaped Region of

Interest for Planning in Localized Prostate Cancer, International Journal of Radiation

Oncology*Biology*Physics, vol. 78, no. 3, p. S377, Nov. 2010.

(14) C. Lafond et al., (Which IMRT? From step and shoot to VMAT: physicist point of view),

Cancer Radiothrapie: Journal De La Socit Franaise De Radiothrapie Oncologique , vol.

14, no. 6, pp. 539-549, Oct. 2010.

(15) I. Latorzeff, J. Mazurier, C. Boutry, P. Dudouet, P. Richaud, and R. de Crevoisier, (Benet

of intensity modulated and image-guided radiotherapy in prostate cancer), Cancer

Radiothrapie: Journal De La Socit Franaise De Radiothrapie Oncologique, vol. 14, no.

6, pp. 479-487, Oct. 2010.

(16) Y. Ma et al., Hypofractionated stereotactic radiotherapy for brain metastases: a dosimetric

and treatment efciency comparison between volumetric modulated arc therapy and intensitymodulated radiotherapy, Technology in Cancer Research & Treatment, vol. 9, no. 5, pp. 499-

507, Oct. 2010.

(17) S. D. McGrath, M. M. Matuszak, D. Yan, L. L. Kestin, A. A. Martinez, and I. S. Grills,

Volumetric modulated arc therapy for delivery of hypofractionated stereotactic lung

radiotherapy: A dosimetric and treatment efciency analysis, Radiotherapy and Oncology:

Journal of the European Society for Therapeutic Radiology and Oncology, vol. 95, no. 2, pp.

153-157, May. 2010.

(18) C. Men, H. E. Romeijn, X. Jia, and S. B. Jiang, Ultrafast treatment plan optimization for

volumetric modulated arc therapy (VMAT), Medical Physics, vol. 37, no. 11, pp. 5787-5791,

Nov. 2010.

(19) A. Y. Minn et al., Comparison of intensity-modulated radiotherapy and 3-dimensional

conformal radiotherapy as adjuvant therapy for gastric cancer, Cancer, vol. 116, no. 16, pp.

3943-3952, Aug. 2010.

(20) K. Otto, Volumetric modulated arc therapy: IMRT in a single gantry arc, Medical Physics, vol.

35, no. 1, pp. 310-317, Jan. 2008.

(21) D. Palma et al., Volumetric modulated arc therapy for delivery of prostate radiotherapy:

comparison with intensity-modulated radiotherapy and three-dimensional conformal

radiotherapy, International Journal of Radiation Oncology, Biology, Physics, vol. 72, no. 4, pp.996-1001, Nov. 2008.

(22) C. C. Popescu et al., Volumetric modulated arc therapy improves dosimetry and reduces

treatment time compared to conventional intensity-modulated radiotherapy for locoregional

radiotherapy of left-sided breast cancer and internal mammary nodes, International Journal

of Radiation Oncology, Biology, Physics, vol. 76, no. 1, pp. 287-295, Jan. 2010.

(23) J. Qiu, Z. Chang, Q. J. Wu, S. Yoo, J. Horton, and F. Yin, Impact of volumetric modulated

arc therapy technique on treatment with partial breast irradiation, International Journal of

Radiation Oncology, Biology, Physics, vol. 78, no. 1, pp. 288-296, Sep. 2010.


33/36



31

(24) S. Rosenthal et al., Comparison of Volumetric Modulated Arc Therapy (VMAT) vs. Fixed Field

Intensity Modulated Radiation Therapy (IMRT) Techniques for the Treatment of Localized

Prostate Cancer, International Journal of Radiation Oncology*Biology*Physics, vol. 78, no. 3,

p. S755, Nov. 2010.

(25) M. Scorsetti et al., Early clinical experience with volumetric modulated arc therapy in head

and neck cancer patients, Radiation Oncology (London, England), vol. 5, p. 93, 2010.

(26) R. Shaffer et al., Volumetric modulated Arc therapy and conventional intensity-modulated

radiotherapy for simultaneous maximal intraprostatic boost: a p

110706 faculty position paper on vmat-web

Documents