September 9, 2013
I am Brandel France de Bravo, and I am speaking on behalf of the Cancer Prevention and Treatment Fund of the National Research Center for Women & Families. Our non-profit research center scrutinizes medical data, evaluating scientific evidence of benefits and risks for patients. We analyze and review research and provide objective and understandable health information to patients, health care providers, and policy makers. Our organization does not accept funding from companies that make medical products, and therefore I have no conflict of interest.
The research presented in the FDA summary makes clear five points that are essential in considering the benefits and safety of Computed Tomography Colonography or CTC:
1) There is NO ONE method of screening asymptomatic patients for colon cancer that meets the three necessary criteria for increasing compliance with screening guidelines: that the method be highly accurate; very low risk; and involve little to no discomfort—either physical or psychological – including the “yuck” factor. Optical colonoscopy has not been as widely embraced as many health experts would have liked, except perhaps by unscrupulous surgical centers, which The New York Times reports are charging insurance companies as much as $6,000. The Times noted that colonoscopies “are the most expensive screening test that healthy Americans routinely undergo — and often cost more than childbirth or an appendectomy in most other developed countries.” While traditional colonoscopy has downsides, it at least offers a “two-for”: it screens patients for colon cancer and removes potentially pre-cancerous polyps all in the same procedure.
2) Virtual colonoscopies don’t screen and treat; they just screen, which is why the term “virtual colonoscopy” is a misnomer. It is, however, a great marketing tool as it implies a clean, no-muss-no-fuss approach. In fact, patients still have to go through the grueling process of bowel preparation.
3) CTC is not as good as optical colonoscopy at detecting polyps or lesions of 10 mm or smaller. This, however, may not be so important given that polyps under 10mm are less likely to be suspicious and in need of removal. Smaller polyps grow slowly, and some will even shrink and disappear on their own.
4) While CTC is less sensitive for smaller lesions and exposes patients to relatively high doses of radiation, it does offer one major benefit over colonoscopy: it reduces the risk of major bleeding and disease transmission—both of which are of particular concern in older patients.
5) Besides exposing patients to radiation and missing smaller polyps, CTC opens a Pandora’s box of “extra-colonic findings”—suspicious findings in nearby organs. These findings can lead to more diagnostic tests, some of which may be invasive or harmful, but they also sometimes save lives.
While radiologists often dismiss worries about excessive exposure to radiation, our Center continues to be concerned because so many patients are being exposed to radiation from so many different medical tests, as discussed today by Dr. Berrington de González. Two pieces of information or safeguards that would help make the decision about CTC easier are missing:
- We need to know if patients in the U.S. are more likely to undergo regular screening with so-called virtual colonoscopies than regular ones. This is the purpose of patient-centered outcomes research—how do real patients in the real world respond to these two options, and what are the benefits of each in attracting patients who should get screened?Dr. Summers shared data on patient acceptance, showing a preference for CTC, but that data was based on answers to questionnaires—given either after the procedure or about a hypothetical screening. To date there are no studies in the U.S. where asymptomatic patients who have never before been screened are given a choice between CTC and regular colonoscopy and then actually undergo their preferred screening.
- When is a professional society or government agency going to address the health threat of increased lifelong exposure to radiation from medical tests and treatments? The advent of electronic medical records provides the opportunity to implement a plan to reduce patients’ total exposure to radiation. It wouldn’t cap exposure but rather allow providers to make informed decisions: by enabling them to review a patient’s previous radiation exposure before choosing what kind of screening to recommend. For example, a heavy smoker undergoing regular CT scans for her lungs should probably be screened with colonoscopy rather than CTC, since the latter also exposes part of the lungs to radiation.
There are no easy answers, but we trust the US Preventive Services Task Force to stay on top of this important issue, providing unbiased information on the risks and benefits as new data become available. We agree with the Task Force that at this point, there is no reason to recommend virtual colonoscopies for most patients who need screening. We would add, however, that if specific patients are unwilling to undergo regular colonoscopies, then a virtual colonoscopy is a reasonable alternative.