Test for Blood in Stool May Help Prevent Colon Cancer
A widely available standard test that detects bleeding in the stomach or bowel (gastrointestinal tract) may help prevent the development of colon cancer. The results, published in the November 30, 2000, issue of the New England Journal of Medicine, showed that persons who underwent an FOBT (fecal occult-blood test) and received further evaluation were less likely to develop colon cancer than people who did not undergo the test.
The FOBT looks for occult or hidden blood in the stool (feces), which usually indicates bleeding in the gastrointestinal tract. Sometimes this bleeding may be a sign of cancer or a precancerous lesion known as a polyp, which can be removed to prevent cancer.
Previous studies have shown that the FOBT decreases the number of deaths from colon cancer, probably by detecting early cancers, which are more easily treated. This led scientists to wonder if this test might actually prevent the development of colon cancer.
To figure this out, researchers enrolled people without a history of colon cancer in the Minnesota Cancer Control Study in the mid-1970s. Approximately 46,000 participants were randomly assigned to one of three groups: screening once a year (annual), screening once every two years (biennial), or usual care (control group). If a FOBT showed blood in the stool, the participants were then advised to undergo further diagnostic tests including colonoscopy or a combination of barium enema and sigmoidoscopy.
After following participants for 18 years, the study found that patients in the two screening groups developed fewer new colon cancers as compared with the control group. People screened annually developed 20 percent fewer colon cancers compared to the control group, while people screened biennially had 17 percent fewer colon cancers. The researchers believe the screening allowed precancerous lesions to be found and removed before they developed into cancer.
While this new evidence supports the idea that screening for colon cancer is beneficial, the debate goes on about what type of tests to use, when to start and how frequently people should undergo these tests. An ongoing screening study (the Prostate, Lung, Colorectal and Ovarian Screening Trial) sponsored by the NCI may shed light on some of these issues. An editorial in the same issue of the New England Journal discusses the screening controversy and comments that while the risk and benefits of colon cancer screening need to be considered, 60 percent of people eligible for screening in the U.S. have never had it done. The editorial concludes that until the "preferred" test is defined, having some kind of colon cancer screening test is probably better than having no screening at all.
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