anatomy-based mlc field optimization for the treatment of gynecologic malignancies

Anatomy-based Anatomy-based MLC Field Optimization MLC Field Optimization

for the Treatment of for the Treatment of Gynecologic MalignanciesGynecologic Malignancies

Myriam Bouchard M.D.Myriam Bouchard M.D.Nadeau S, Germain I, Raymond P.E., Nadeau S, Germain I, Raymond P.E., Harel F, Beaulieu F, Beaulieu L, Roy R, Harel F, Beaulieu F, Beaulieu L, Roy R, Gingras LGingras L

Dep. of radiation oncology of L’Hotel-Dieu de Quebec, Dep. of radiation oncology of L’Hotel-Dieu de Quebec, QC, Canada QC, Canada Dep. of Physics, Physics Engineering and Optics, Laval Dep. of Physics, Physics Engineering and Optics, Laval University, Quebec, CanadaUniversity, Quebec, Canada

Myriam Bouchard M.D.Myriam Bouchard M.D.ASTRO 2005ASTRO 2005

IMRT for GYN IMRT for GYN malignanciesmalignancies

Mundt Mundt et alet al.(Chicago, 2000).(Chicago, 2000)Portelance Portelance et alet al.(St. Louis, 2001).(St. Louis, 2001)Heron Heron et alet al.(Pittsburgh, 2003).(Pittsburgh, 2003)Lujan Lujan et alet al.(Chicago, 2003).(Chicago, 2003)D’Souza D’Souza et alet al. (Houston, 2005). (Houston, 2005)

Adequate target coverageAdequate target coverageOARs sparingOARs sparing

Small bowelSmall bowel RectumRectum BladderBladder Bone marrowBone marrow



Post-operativePost-operative whole-pelvis whole-pelvis radiotherapyradiotherapy– More bowel to spare, bowel replacing More bowel to spare, bowel replacing

uterusuterus– Less organ motionLess organ motion

Good clinical results with IMRT Good clinical results with IMRT 11 – 36 patients, whole-pelvis IMRT36 patients, whole-pelvis IMRT

Median follow-up = 19,6 monthMedian follow-up = 19,6 month

– 13.9% less GI-GII toxicity13.9% less GI-GII toxicity1 MUNDT et al. IJROBP, vol.56 #5 (2003) pp.1354-1360



Disadvantages of IMRTDisadvantages of IMRT– Large number of segments and MULarge number of segments and MU

Increased scattered doseIncreased scattered dose Dose calculation uncertaintiesDose calculation uncertainties

– Higher potential impact of machine or Higher potential impact of machine or patient positioning errors patient positioning errors

– Increased planning, treatment and Increased planning, treatment and quality assurance timequality assurance time

– Higher impact of organ motionHigher impact of organ motion

BallistaBallistaA new inverse planning A new inverse planning

approachapproach

A dosimetric studyA dosimetric studyApproved by the local institutional committee for medical Approved by the local institutional committee for medical ethicsethics


ObjectivesObjectives EvaluateEvaluate Ballista Ballista as an alternative as an alternative

– Between 4-field and IMRTBetween 4-field and IMRT

– For post-operative whole-pelvis For post-operative whole-pelvis radiotherapy in gynecologic radiotherapy in gynecologic malignanciesmalignancies


HypothesisHypothesis Same target coverageSame target coverage

Organs at risk (OARs) sparingOrgans at risk (OARs) sparing– Better than 4-field Better than 4-field – As good as IMRT ?As good as IMRT ?

Treatment delivery advantagesTreatment delivery advantages


Materials and methodsMaterials and methods 10 patients10 patients

Endometrial or cervix malignanciesEndometrial or cervix malignancies

Post-operative external Post-operative external radiotherapyradiotherapy

45 Gy / 25 fractions, whole-pelvis45 Gy / 25 fractions, whole-pelvis


Materials and methodsMaterials and methods

For comparison purposes For comparison purposes

4 plans created for each patient4 plans created for each patient

Conventional 4-fieldConventional 4-field Enlarged 4-fieldEnlarged 4-field

– Results for OARs at same PTV Results for OARs at same PTV coveragecoverage

IMRTIMRT BallistaBallista

Inverse planning

Materials and Materials and methodsmethods

Forward planningForward planning

4-field4-field

enlarged 4-fieldenlarged 4-field


Materials and methodsMaterials and methods Planning CTscan as usualPlanning CTscan as usual

Conventional planning : Conventional planning : – 4-field plans based on bony landmarks4-field plans based on bony landmarks– Created before other plan conceptionCreated before other plan conception

Enlarged 4-fieldEnlarged 4-field– Aperture shaped to PTVAperture shaped to PTV

Materials and Materials and methodsmethods

Inverse planningInverse planning

IMRTIMRT

BallistaBallista


CTV (ITV)CTV (ITV) External iliac nodesExternal iliac nodes Internal iliac nodesInternal iliac nodes Obturator nodesObturator nodes Presacral regionPresacral region 1/2 superior vagina1/2 superior vagina ParametersParameters

Vessels + 5 mm

ITV 1 cm


CTV / ITVCTV / ITV


3D CTV3D CTV


PTV = CTV + 1 cmPTV = CTV + 1 cm


OARsOARs Bowel (colon + small bowel)Bowel (colon + small bowel)

– Region at risk to find bowelRegion at risk to find bowel

= RAR-B= RAR-B RectumRectum BladderBladder Bone marrowBone marrow


Bowel / RAR-BBowel / RAR-B


IMRTIMRT Plans created with PinnaclePlans created with Pinnacle3 3

systemsystem Step-and-shootStep-and-shoot 7 coplanar and equidistant 6 MV 7 coplanar and equidistant 6 MV

beamsbeams– 1 extraction1 extraction– 10-12 intensity levels10-12 intensity levels– Minimum field area = 4 cmMinimum field area = 4 cm22


BallistaBallista 1 1

Inverse planning systemInverse planning system – Recently developed at L’Hotel-Dieu de Recently developed at L’Hotel-Dieu de

QcQc Simultaneous optimizationSimultaneous optimization

– Gantry, table and collimator anglesGantry, table and collimator angles– Wedge angle and beam weightsWedge angle and beam weights

Intensity modulationIntensity modulation– Anatomy-based MLC fieldsAnatomy-based MLC fields

1 BEAULIEU et al. Med.Phys.31, 1546-1557 (2004)


Anatomy-based fieldsAnatomy-based fields


• Number of fields• Gantry and table angle optimization

Feasibility

Selection of a fixed geometry (class solution)

Steps Result / conclusion

• Addition of sub- anatomic structures

New treatment that is comparable to IMRT

BallistaBallista


Beam orientation for Beam orientation for Ballista Ballista plansplans

9 beams

23 MV


• Number of fields• Gantry and table angle optimization

Feasibility

Selection of a fixed geometry (class solution)

Steps Result / conclusion

• Addition of sub- anatomic structures

New treatment that is comparable to IMRT

BallistaBallista


Sub-anatomic Sub-anatomic structuresstructures


AnalysisAnalysis

For each plan (4) created For each plan (4) created for each patient (10)for each patient (10)

DVH DVH – PTV and OARsPTV and OARs

Number of segmentsNumber of segments Number of MUNumber of MU

Statistics : Student’s paired Statistics : Student’s paired tt-test-test

ResultsResults

Target coverageTarget coverage


4-field Enlarged 4-field

IMRT Ballista


PTV coverage / PTV coverage / homogeneityhomogeneity

4-field Enlarged4-field

IMRT Ballista

77%

p =0.03

(Mean±SEM, n=10)

ResultsResults

OARs sparingOARs sparing


RAR-B RAR-B 40 and 45 Gy40 and 45 Gy

+ 34.7 %


IMRT Ballista

(Mean±SEM, n=10)

For the same PTV coverage


RAR-BRAR-B


IMRT Ballista

+ 20.8 %

Ballista vs 4-field : V45 Gy, p < 0,001

(Mean±SEM, n=10)


RAR-BRAR-B

(Mean±SEM, n=10)

45 Gy : p = 0.15

40 Gy : p < 0.001 (diff. = 61.4 cm3 or 9.9% )


IMRT Ballista

(Mean±SEM, n=10)


Rectum – mean V 45 Rectum – mean V 45 GyGy

4-champs4-champs IMRTIMRT BallistaBallista p valuep value(difference)(difference)

61.7 %61.7 % 50.0%50.0% 59.9%59.9% NSNS(1.8%)(1.8%)


Rectum – mean V 45 Rectum – mean V 45 GyGy


61.7 %61.7 % 50.0%50.0% 59.9%59.9% SSSS(9.9%)(9.9%)


Bladder – mean V 45 Bladder – mean V 45 GyGy


91.3%91.3% 46.0%46.0% 47.8%47.8% SSSS(43.5%)(43.5%)


Bladder – mean V 45 Bladder – mean V 45 GyGy


91.3%91.3% 46.0%46.0% 47.8%47.8% NSNS(1.8%)(1.8%)


OARs OARs V47.25 V47.25 GyGy

MeanMeanVV47.2547.25 GyGy

4-field4-field EnlargeEnlargedd

4-field4-field


RAR-BRAR-B 3.4%3.4% 1.6%1.6% 9.2%9.2% 6.7%6.7%


OARs OARs V47.25 V47.25 GyGy

MeanMeanVV47.2547.25 GyGy

4-field4-field EnlargeEnlarged 4-fd 4-f


RectumRectum 0.1%0.1% 5.6%5.6% 4.6%4.6% 7.3%7.3%

BladderBladder 1.4%1.4% 10.0%10.0% 20.3%20.3% 18.8%18.8%


Bone marrowBone marrowDoses moyennes - moelle osseuse

V40Gy; 27,8

V40Gy; 46,2

V40Gy; 32,5 V40Gy; 36,4

0,010,020,030,040,050,060,070,080,090,0

100,0

4-champs 4-champs élargi IMRT Ballista

Vo

lum

e (%

)

V10Gy

V20Gy

V30Gy

V40Gy

V45Gy

V47.25Gy

4-field Enlarged 4-field

IMRT Ballista(Mean±SEM, n=10)

Enlarged 4-field vs Ballista : V40 Gy, p < 0,001 (for the same PTV coverage)


V 50% and V 95%V 50% and V 95%

0

2000

4000

6000

8000

10000

12000

1

Vol

ume

(cc)

4-champs

4-champs élarg.

IMRT

Ballista

Volume traitéVolume irradiéIrradiated volume Treated volume

4-field

Enlarged 4-f

(Mean±SEM, n=10)

ResultsResults

Treatment deliveryTreatment delivery


Number of segmentsNumber of segments

4-field4-field EnlargedEnlarged

4-field4-fieldIMRTIMRT BallistaBallista

44 44 128.6 ± 0.8 128.6 ± 0.8 33.3 ± 0.7 33.3 ± 0.7

(Mean±SEM, n=10)


Number of MUNumber of MUM

on

itor

Un

its

4-field

(Mean±SEM, n=10)


Calculated / delivered Calculated / delivered dosesdoses

Impact of leaf position errorsImpact of leaf position errors

± 1.4 Gy

DiscussionDiscussion


Dose constraint on Dose constraint on OARsOARs

Priorities in our studyPriorities in our study First priority on RAR-BFirst priority on RAR-B Bladder Bladder

– Relative important weight given to it…Relative important weight given to it… Organ motion +++Organ motion +++ Eventually replaced by small bowelEventually replaced by small bowel

Bone marrow : when possibleBone marrow : when possible


OARs resultsOARs results Bone marrow resultsBone marrow results

– Worse compared to conventional Worse compared to conventional planningplanning but PTV coverage not optimalbut PTV coverage not optimal

– Similar gains IMRT vs BallistaSimilar gains IMRT vs Ballista


OARs resultsOARs results

To enhance sparing…To enhance sparing… Organ motion study necessary Organ motion study necessary 22

– To limit as possible expansion for PTVTo limit as possible expansion for PTV In our study, ITV/PTV limited sparing of In our study, ITV/PTV limited sparing of

rectum rectum

Optimal patient immobilizationOptimal patient immobilization– essentialessential

2 AHAMAD et al. (MDACC). IJROBP 62 (4) p.1117-1124 (2005)


Advantages Advantages BallistaBallista vs IMRTvs IMRT

Number of segments reduced by Number of segments reduced by 75%75%

Number of MU reduced by 55%Number of MU reduced by 55%

Result in scattered radiation– risk of second malignancies


Advantages Advantages BallistaBallista vs IMRTvs IMRT

Dose calculation + precise and + Dose calculation + precise and + robustrobust

treatment time treatment time (door-to-door)(door-to-door)

– 40-45 min IMRT – 20-25 min Ballista

quality assurance timequality assurance time– Dosimetric QA measurements can be Dosimetric QA measurements can be

avoidedavoided Larger segmentsLarger segments


Class solutionClass solution Statistic analysis on each beam’s roleStatistic analysis on each beam’s role

– Frequency of utilization of beamFrequency of utilization of beam To spare a determined (part of) OARTo spare a determined (part of) OAR To irradiate a part of the PTVTo irradiate a part of the PTV

Class solution based on «beam’s role»Class solution based on «beam’s role»

Similar plans created without Similar plans created without BallistaBallista Similar planning with other system is possibleSimilar planning with other system is possible

ConclusionsConclusions

BallistaBallistaA new inverse planning approachA new inverse planning approach


Conclusions – Conclusions – BallistaBallista PTV coverage improvedPTV coverage improved

OARs sparingOARs sparing– Similar to IMRT planningSimilar to IMRT planning– Except for the rectum,Except for the rectum, not as good as not as good as

IMRTIMRT Similar to conventional 4-fieldSimilar to conventional 4-field Under tolerance dosesUnder tolerance doses


Conclusions – Conclusions – BallistaBallista Advantages Advantages BallistaBallista vs IMRT vs IMRT

– Better dose calculation Better dose calculation – Less treatment timeLess treatment time– Less scattered doseLess scattered dose– Less quality assurance timeLess quality assurance time


PerspectivesPerspectives Clinical results to comeClinical results to come

– Feasibility studyFeasibility study– 15 patients treated 15 patients treated

whole-pelvis after resection of gynecologic whole-pelvis after resection of gynecologic malignanciesmalignancies

AcknowledgmentsAcknowledgments

To Sylvain Nadeau, medical physicistTo Sylvain Nadeau, medical physicisttoto Radiation oncologists Radiation oncologists

to Physiciststo Physicists to Radiation to Radiation therapiststherapists

anatomy-based mlc field optimization for the treatment of gynecologic malignancies

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