whole body screening – risks and benefits
TRANSCRIPT
WHOLE BODY SCREENING – RISKS AND BENEFITS Wan Najwa Zaini Wan Mohamed, Radiologist, JPD HQE 2
US AIRPORT’S WHOLE BODY IMAGING
US AIRPORT’S WHOLE BODY IMAGING
Problems:•Privacy Concerns•Health Concerns•Scanner Effectiveness•Security Delays•Staff Requirements, Workload
US AIRPORT’S WHOLE BODY IMAGING•Nov 2010 Campaign - Stop whole body imaging in U.S. airports! Join National Opt-Out Day •2013 – 250 backscatter scan machines removed from US airports
WHOLE BODY SCREENING
1. INTRODUCTION2. PRINCIPLES IN SCREENING3. RADIATION ISSUES IN CT4. COST ISSUES5. THE DEBATE: THE PROS AND CONS6. CURRENT POLICIES7. THE FUTURE OF WHOLE BODY
IMAGING
Whole Body Screening
INTRODUCTION
INTRODUCTION
Sectional imaging such as Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) have revolutionized the capabilities for imaging, image guided therapeutic intervention and improved targeted radiation therapy.
The CT scan is much more widely available than the MRI
Has benefitted many patients – clinching the diagnosis, guiding surgery, providing a road map, staging a disease more accurately and allowing radiation therapy to proceed more precisely.
INTRODUCTION
Many varieties available – single, spiral, multislice, dual source technology, electron beam CT.
Faster and rapid scan time in millisecond or sub second duration.
Allows elegant multiplanar and 3D reconstructions e.g. Virtual colonoscopy.
Not surprising that CT scan has now been explored and employed in whole body screening programmes – to detect diseases before they become more advanced
INTRODUCTION
First public appearance in a Wall Street Journal article published in early 2000 – reported on the efforts of several radiologists who were seeking to make CT part of preventive medicine programs.
Many CT screening centres have sprouted up based on the promise of wellness screening.
As whole body CT is being marketed directly to consumers, the consumers (patients) are now beginning to demand the test.
INTRODUCTION
Yet, several questions have not been answered adequately for WBCT screening:
1. Large scale randomized clinical trials (RCT) for evaluation of whole body screening in apparently healthy individual has not been published to date.
2. Should intravenous contrast media be used for all whole body screening CT scans?
3. Guidelines that exist for follow up or further evaluation for overall WBCT screening when abnormalities are detected, e.g. callback rate.
INTRODUCTION
4. Cost effectiveness of whole body screening CT
5. Indices for whole body CT such as negative predictive rate, sensitivity, specificity, false negative, false positive and others are unknown.
Whole Body Screening
PRINCIPLES IN SCREENING
PRINCIPLES IN SCREENING
What is a screening test? a test, procedure or investigation that is
used to look for disease before it manifests with signs and symptoms.
can be applied to the whole population or to a subset of the population
is considered effective if it reduces deaths from the disease being screened for
PRINCIPLES IN SCREENING
Main considerations:1. Does the disease merit screening? A disease
that is so slowly progressing that treating it early may not make a difference to the lifespan.
2. Is there a reliable screening test for the disease in question? The false positive and false negative rates, positive and negative predictive values and accuracy are important parameters.
3. Is there available and effective intervention/ treatment for the disease in question, if detected early? No point in screening if there is no cure or effective treatment.
PRINCIPLES IN SCREENING
Therefore, screening should not be taken lightly and requires careful cost-benefit analysis.
For individuals opting for any screening test/procedure/investigation, they should be counseled as to the pros and cons, benefits and risks (if any) entailed in the process.
Whole Body Screening
RADIATION ISSUES IN CT
RADIATION ISSUES IN CT
Estimated effective doses from diagnostic CT procedures: 1 to 10 milliSieverts (mSv)
A CT examination with an effective dose of 10 mSv may be associated with an increased risk of fatal cancer of approximately 1 chance in 2000.
CT scan must only be performed when the benefits outweigh the risks
RADIATION ISSUES IN CT
The amount of radiation dose received by the patient is variable by a factor of 10, depending on the patient’s size, make and type of CT scanner, scanning parameters and body part.
CT studies account for the largest population radiation dose from medical diagnostic studies.
Based on UNSCEAR 2000 Report on Sources And Effects of Ionising Radiation: CT studies are increasing rapidly over the years from 14% in the period 1955-1990 to 33% in the period 1991-1996
Whole Body Screening
COST ISSUES
COST ISSUES
When an abnormality is detected, the follow-up tests and treatment can be costly.
Insurance companies are more likely to cover the cost of further testing if the screening study is positive, but there is no assurance that they will cover the entire cost.
Self-referred whole-body CT itself is not covered.
Undoubtedly will increase overall healthcare expenditures.
COST ISSUES
Whole Body Screening
THE DEBATE: THE PROS AND THE CONS
THE DEBATE: THE PROS AND THE CONS Researchers, physicians and healthcare
administrators across the globe are engaging in healthy scientific discourse about the controversies and issues surrounding whole-body CT screening.
Experts participated in a recent panel discussion on CT screening at the 2002 scientific assembly and annual meeting of the Radiological Society of North America (RSNA 2002), and research studies on the topic continue to be published in scientific and medical journals.
THE PROS
Dr. Michael Brant-Zawadzki, a radiologist with wide experience in targeted CT screening as well as whole-body CT, has found that in screening self-referred patients older than 40 years, about one in a hundred will be found to have a cancer.
Cancers of the lung and kidney are among the most common to be detected, but pancreatic cancer, potentially dangerous lesions of the abdominal aorta called aneurysms, and lymphoma,, also have been found by screening CT (RadioGraphics 2002;22:1532-39).
THE PROS
Dr. Brant-Zawadzki cites a study carried out at the Mayo Clinic reporting that, when CT screening for lung cancer was extended to the pelvic region, 14% of those examined were found to have clinically significant abnormalities.
THE CONS
Dr. E. Stephen Amis Jr., estimates that as many as 80 percent of abnormalities detected by whole-body CT may not be life-threatening.
In a study presented at RSNA 2002, more than one-third of nearly 1,200 patients were referred for follow-up studies (Casola et al.). These patients may suffer considerable anxiety, and some of the follow-up tests themselves involve an element of risk.
THE CONS
Surgery, for instance, carries risks of an adverse reaction to anesthesia, bleeding, infection, and scarring.
Additional radiologic exams increase total radiation exposure, and there is a chance of an allergic reaction if contrast material is injected.
The other major concern about whole-body CT is that a reading of "normal" may be incorrect and, as a result, patients will be falsely reassured (false negative).
THE CONS
The fact that no intravenous contrast material is used in whole-body CT has been held out as an advantage, but non-contrast scans of the abdomen and pelvis provide only limited information. Small lesions in the liver, kidneys, or pancreas may readily be missed.
There is good reason not to screen persons younger than 40 years, as the yield of significant disease will be extremely low.
Whole Body Screening
CURRENT POLICIES
CURRENT POLICIES
In all medical procedures, there must be indications and justification for its use.
Consideration of the available resources versus clinically useful information that alters management inclusive of financial and safety issues cannot be compromised.
This is even more imperative with medical procedures requiring ionizing radiation.
CURRENT POLICIES
Justification, Optimisation and Dose Limitation remains the main tenets for radiology practitioners.
In clinical scenarios where benefit exceeds risks and further management of the patient is dependent on information gleaned from the CT scan, then the examination is deemed justified.
CT scans should be performed keeping in mind the principle of ALARA.
CURRENT POLICIES
Where CT may be considered appropriate for screening: Cardiac – Calcium scoring, CT Angiogram Colon– Virtual Colonography Lung – still controversial
Targeted CT screening procedures
CURRENT POLICIES
Targeted CT screening procedure CT Cardiac – Calcium scoring
most useful for patients with a medium risk level for coronary artery disease
total calcium score greater than 400 HU (by Agatston method)
Cardiac CT Angiogram to detect significant coronary artery stenosis only asymptomatic and low to moderate
cardiovascular risk patients with positive stress ECG
CURRENT POLICIES
CT Colonography (Virtual Colonoscopy) radiation dose ranges from 1.8mSv to 15
mSv. average 8 mSv (barium enema 7 mSv). to detect polyps and early colonic cancers Can be considered if part of a programme
for colorectal cancer screening For average-risk individuals 50 years and
older
CURRENT POLICIES
CT Lung to detect early lung cancers Still controvertial even if applied in high
risk individuals (e.g. smokers) ongoing trials in screening lung CT in the
at risk population for example the National Lung Screening Trial in the USA
CURRENT POLICIES
Whole Body Screening in the Healthy/ Asymptomatic Individual
To date, the College of Radiology (CoR) does not see any clear benefit from whole body screening CT scans in healthy individuals.
The CoR does not recommend whole body screening CT scan including routine CT lung in healthy asymptomatic individuals in the absence of risk factors as the risks outweigh the potential benefits.
CURRENT POLICIES
The appropriateness of CT screening examinations may change with new evidence, improvements or changes in CT technology, disease pattern, type, treatment and various other factors.
The American College of Radiology (ACR) believes that there is insufficient evidence showing that whole-body CT screening prolongs life or is cost-efficient.
CURRENT POLICIES
The ACR takes the position that whole-body CT cannot be recommended for those who lack symptoms and who have no family history of disease.
Many findings that will not affect patients' health will nevertheless cause anxiety, lead to unnecessary follow-up examinations and treatments, and waste money.
The U.S. Food and Drug Administration (FDA) concurs that whole-body CT has not been convincingly shown to detect disease early enough to spare patients from serious illness or premature death.
CURRENT POLICIES
Even if such benefit is demonstrated, states the FDA, it might not be great enough to offset potential harm from screening.
The FDA has said that a CT finding of abnormality despite the absence of significant disease is far likelier than the discovery of actual life-threatening disease.
Even if a serious condition is found, the patient will benefit only if there is effective treatment and if the disease is found early enough to respond to this treatment.
CURRENT POLICIES
Whole Body Screening
THE FUTURE OF WHOLE BODY SCREENING
THE FUTURE OF WHOLE BODY SCREENING New CT scanners currently under development
will reduce the amount of radiation. If screening is limited to persons older than 50 years, exposing children or women of childbearing age will not be an issue.
Future scanning may routinely include the use of oral and intravenous contrast material. Results could be reported to a central database so as to better determine the effectiveness of whole-body CT.
THE FUTURE OF WHOLE BODY IMAGING MRI Superior to CT in many ways But, more expensive, not readily
available in all centres, time consuming, difficult to perform
Imaging of the lung was suboptimal However, with the recent breakthrough
in MR technology, whole body, high-quality MRI screening is now feasible.
THE FUTURE OF WHOLE BODY IMAGING the MR systems manufactured nowadays
allow much faster imaging of the entire body, while maintaining high image quality that even machines made 1 year ago did not possess.
Basically, new designs of transmit-receiver coils, easier movement of the imaging table, and new data-acquisition techniques have allowed rapid imaging of the entire body as well as acceptable image quality of the lungs.
THE FUTURE OF WHOLE BODY IMAGING High-quality, whole body MRI imaging that
would take 2 hours even 1 year ago now can be done in 10-15 minutes, making the technique very suitable for rapid, highly accurate whole body imaging in an easily tolerable time frame.
It remains to be seen if the public will demand screening with whole body MRI because of its superiority of disease detection and higher safety than that offered by CT.
THE FUTURE OF WHOLE BODY IMAGING
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