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Opinion |
1 Department of Radiology, Boston University School of Medicine, Boston Medical Center, 88 E. Newton St., Boston, MA 02118.
Received November 11, 1999;
accepted after revision November 23, 1999.
Address correspondence to J. T. Ferrucci.
Introduction
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Introducing a fundamentally new method for early detection of such a common and important neoplasm as colorectal cancer presents a crucial challenge and unique opportunity for radiologists. That endoscopic removal of colonic polyps reduces mortality from colorectal cancer is now widely accepted, but the roles of sigmoidoscopy and colonoscopy, although vital, are now possibly threatened. Diagnostic methods that have been standard practice in the past (digital rectal examination, fecal occult blood, sigmoidoscopy, colonoscopy, and barium enema) will be impacted and possibly displaced by CT colonography. Concerns and controversies will arise. If these issues could be anticipated and addressed, perhaps on the basis of past experience with the promotion of breast cancer screening, acceptance of CT colonography might be hastened. Does the specialty of radiology have a useful precedent to guide us? Indeed, it does. Radiologists have gained valuable insights during the decades of development of mammography as the fundamental breast cancer screening technique. The question arises as to what lessons can be learned from the efforts with mammography that will be useful in introducing CT colonography for colorectal cancer screening. I believe there are clinical, technical, and political lessons.
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Compare and Contrast with Alternative Tests
Screening recommendations circulated by major health organizations such as
the American Cancer Society, American College of Physicians, and Office of
Technology Assessment must be learned. The importance of risk-stratification
profiles, cost-benefit models of colorectal screening, and research
initiatives in colorectal neoplasm detection, including genetic stool
sampling, must all be studied. Because CT colonography will be a competitive
alternative to flexible sigmoidoscopy, conventional colonoscopy, and
double-contrast barium enema, radiologists need to understand the strengths
and weaknesses of all the colorectal screening tests to propose CT
colonography as a screening strategy. Access, performance, risks, benefits,
and costs of these methods must all be evaluated.
For example, a key issue is the justification of conventional colonoscopy as a screening test. The size and histologic criteria that constitute a significant polyp and the overall cost to society incurred by detection and removal of such polyps are uncertain. In fact, in a recent control study one third of the "polyps" resected by colonoscopy were found to be merely hyperplastic at histology [2]; their removal provided no patient benefit in terms of cancer prevention. These are legitimate concerns radiologists attempting to introduce CT colonography must raise and discuss. Many impartial observers believe colonoscopists have overstated their case. If so, radiologists have to prove that CT colonography is the better screening technique.
Assure Competence
As with mammographic interpretation, radiologic scientific societies and
national organizations such as the American College of Radiology have an
early, immediate, and continuing opportunity to train and measure competence
of radiologists and assure the public that interpreters are highly skilled.
Not only gastroenterologists but, more important, the third-party payers,
government regulators, and public will demand no less. Our extraordinary
success and proud legacy of the American College of Radiology's mammography
facility accreditation program led to the Food and Drug Administration's
Mammography Quality Standards Act, an ideal template. Not only is this
opportunity compelling, but also it is an obligation that we must fulfill.
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Streamline Examination Techniques
As with the gradual emergence of a screening mammographic examination
distinct from a diagnostic study, a standardized, simplified, and streamlined
screening CT colonographic examination will need to evolve to gain wide
acceptance. The examination will have to be performed quickly, comfortably,
and without the need for a radiologist to be present. This will undoubtedly
mean that IV agents for spasmolytic bowel relaxation (glucagon) and
complicated gas insufflation protocols using tanks of carbon dioxide will have
to be eliminated or significantly simplified. Moreover, as with screening
mammograms, the need for off-line batch interpretation and lower charges is
obvious.
Maximize Specificity
Currently, one of the major drawbacks of mammography is the exceptionally
high level of false-positive results (i.e., low specificity). Indeed, the
relative tolerance of the public and payers of the 70-80% rate of negative
breast biopsy procedures is remarkable. CT colonography, at least in its early
stages, seems to have a far better specificity record (false-positive results
ranging from 10% to 15%) [1,
2]. Thus, retained fluid and
fecal material, complex haustral folds, and image artifacts are, in general,
recognized readily [5]. As with
false-positive mammographic results, the resulting cost and risk of needlessly
precipitated colonoscopies will become a major concern if specificity is lower
[9].
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Promote Affordable Screening
CT colonography must be affordable. As with screening mammography, we need
to create a specific reimbursement code and lower reimbursement formulas to
differentiate screening virtual colonoscopy from diagnostic abdominal and
pelvic CT. This differentiation has had a positive impact on promoting breast
imaging services, although its potential negative effect on total revenues
from breast imaging has become a concern. The political reality is that a
special pricing strategy will be imperative in the short term.
Ally with Interest Groups
Special interest groups in favor of colon screening and the potential of CT
colonography as a new screening technique are quickly emerging. Supporters of
CT colonography as a low-cost and effective method have already been
identified among primary care providers, payers, and patients. However, some
colonoscopists are skeptical of CT colonography. Radiologist proponents of CT
colonography need to be familiar with these various groups and respond
thoughtfully.
Be an Advocate for Prevention of the Disease, Not Just for the
Test
Above all, a successful strategy for radiology will be one that promotes
the overall concept of colon screening to reduce the mortality rate of
colorectal cancer. Reducing deaths from breast cancer has been a more
compelling cause than merely promoting mammography. Parochial salesmanship of
CT colonography as a single test will be a shortsighted strategy unless the
larger goal of preventing colorectal cancer mortality remains in focus. Senior
radiologists have served as able leaders of national breast cancer prevention
programs through their contributions in mammography. We should be prepared to
lead again if and when CT colonography contributes to colorectal cancer
prevention.
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