Eventually, colon cancers bleed and so tests for blood in stool seem an inexpensive and noninvasive alternative to traditional colonoscopies. In fact, a recent article in the journal Cancer Prevention Research showed that fecal immunochemical testing (FIT) is an accurate predictor of colorectal cancer and can provide a low-cost screening alternative for medically underserved populations.
However, Tim Byers, MD, MPH, associate director for prevention and control at the University of Colorado Cancer Center and professor of epidemiology at the Colorado School of Public Health, says that despite its ease, low cost, and one-time accuracy, FIT remains inferior to colorectal cancer screening the old-fashioned way, by colonoscopy.
"Testing for blood in the stool can find cancer and advanced adenomas, but it does not work well for finding most adenomas, therefore creates many missed opportunities for cancer prevention," Byers says. In other words, by the time a colorectal cancer bleeds, the window for successful treatment may be closed -- proverbially, this is discovering the barn door is unlocked after the horse has run away.
To shorten the time before a bleeding colorectal cancer sees treatment, proponents of FIT testing recommend using the procedure yearly, rather than every five-to-ten years as recommended for colonoscopies. Frequent screening, they hope, will allow treatment to follow closely on the heels of the discovery of blood in stool, perhaps with the same timeliness of a colonoscopy, which due to the long time between screenings may catch a cancer that has been on the move for years between checks.
However, "We are very bad in our health care system and as individuals in doing anything yearly, so practices that use FIT testing perform poorly with repeat testing over time -- the poor performance of FIT testing gets even worse as people forget to do the annual tests," Byers says.
In a recent editorial in response to the findings in the above journal, Byers points out that insurance companies have strong incentive to promote the less expensive alternative, but in this case the cheaper alternative may, in fact, lead to fewer colorectal cancers identified in their early stages.
"Tests designed to identify occult blood in the stool are better for detecting colorectal cancer, whereas direct endoscopic visualization of the colorectum [colonoscopy] is better for prevention," Byers writes.
- T. Byers. Examining Stools for Colon Cancer Prevention: What Are We Really Looking for? Cancer Prevention Research, 2011; 4 (10): 1531 DOI: 10.1158/1940-6207.CAPR-11-0410
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