Controversy evident in our guidelines: Yes
The controversy regarding whether to use colonoscopy as a primary screening tool in average-risk subjects is evident in our guidelines. The American College of Gastroenterology recommends that colonoscopy be offered first, whereas the U.S. Preventive Services Task Force recommends a menu of options, with no preference for any single option.
Overall, the literature suggests that offering multiple options simultaneously does not improve screening rates (J. Natl. Cancer Inst. 2005;97:347-57; Med. J. Aust. 2006;184:546-50; Am. J. Gastroenterol. 2004:99:1145-51).
Offering patients a preferred option such as colonoscopy, followed by other options if the patient declines, has been referred to as "sequential testing." Offering the best test first can result in the maximum number of patients screened, and the maximum number screened by the most effective test (Gut 2013;62:735-40).
Dr. Douglas Rex
Although there are no randomized controlled trials to support colonoscopy as a screening test, there is a substantial body of other evidence to support its use for primary screening. First, an initial round of a randomized controlled trial comparing colonoscopy to fecal immunochemical testing (FIT) showed that among patients who underwent screening, colonoscopy detected four times as many patients with advanced adenomas (N. Engl. J. Med. 2012;366:697-706). Available trials indicate that even with operator dependency, colonoscopy outperforms CT and MR colonography for polyp detection. Fecal DNA testing, the only other test with demonstrated sensitivity for serrated lesions, has recently been reported to have greater than 90% sensitivity for cancer in screening, but only 42% sensitivity for advanced lesions, and specificity below 90%. Therefore, the available evidence indicates that colonoscopy is the most effective colon cancer prevention test.
Four case-control studies and two cohort studies have shown reductions in colorectal cancer incidence or mortality with colonoscopy, and the National Polyps Study showed a 53% reduction in colorectal cancer mortality in a population at very high risk for colorectal cancer, compared with the general population (N. Engl. J. Med. 2012;366:687-96). Two recent case-control studies have shown 42%-56% reductions in right colon cancer incidence or death associated with colonoscopy (Ann. Intern. Med. 2011;154:22-30; J. Clin. Oncol. 2012;30:2664-9).
To ensure the competitive future of screening colonoscopy, we should continue to improve colonoscopy as a technology. Returning procedures to the ambulatory surgery center, which typically charges one-third to one-fifth of the charges seen at hospitals, would reduce costs. Reimbursement should be linked to the adenoma detection rate, and we should consider allowing high-level adenoma detectors to use longer intervals between colonoscopy in low-risk patients, and reward them for doing so. Bundled payments that are linked to quality will help improve cost-effectiveness. A return to GI directed sedation, including with propofol, may be incentivized in a bundled payment system. Policies such as "resect and discard" for diminutive polyps will further improve cost-effectiveness. Continuing to emphasize quality is critical to the future of screening colonoscopy.
The United States is the only country in the world with declining incidence rates for colorectal cancer, and this effect may be substantially related to the widespread use of screening colonoscopy. A sequential approach to offering screening tests, with colonoscopy offered first, and other tests offered to those who decline colonoscopy, does not diminish adherence and maximizes screening efficacy.
Douglas K. Rex, M.D., is Distinguished Professor of Medicine, Indiana University School of Medicine, Indianapolis; Chancellor’s Professor, Indiana University–Purdue University Indianapolis; and Director of Endoscopy, Indiana University Hospital.
Should there be a ‘preferred’ CRC screening test? No
There is little debate about the benefits of colorectal cancer screening in average-risk individuals after age 50. There is compelling evidence from randomized controlled trials that fecal blood testing and endoscopic screening (with flexible sigmoidoscopy) are associated with significant reductions in incidence and mortality. Moreover, there is further evidence from the National Polyp Study that detection and removal of cancer precursor lesions (adenomas) are associated with reduced CRC incidence and mortality.
Screening has two primary goals: 1) detection of early-stage cancer, and 2) detection and removal of cancer precursor lesions. Colonoscopy screening offers an opportunity to achieve both goals, with a highly sensitive and specific test. Given the long period for development of adenomas and cancer, a highly sensitive test like colonoscopy can be performed infrequently (every 10 years), requiring fewer reminders compared with less sensitive tests that must be repeated more frequently. Primary screening with colonoscopy has been shown to reduce CRC incidence and mortality in uncontrolled cohort and case-control studies.
There are several important limitations of colonoscopy as a primary screening test. It is the most invasive of screening programs. The risk of serious 30-day adverse events in screening and surveillance ranges from 3/1,000 to 5/1,000 procedures. After age 65, the risk of serious events increases to 7/1,000, and the risk of perforation is 1/1,000. The performance and quality of colonoscopy are operator dependent. There is evidence that low adenoma detection rates are associated with a greater risk of interval cancers within a few years of colonoscopy. Several studies have demonstrated great variability in adenoma detection rate among endoscopists. Quality issues may reduce the overall effectiveness of a colonoscopy screening program.