The Cancer Web Report, What's New In Cancer: January, 1997
Colorectal Cancer

• What to do if small or diminutive polyps are found on sigmoidoscopy? - Sigmoidoscopy is recommended because of its ability to find early cancers and precancerous polyps (adenomas) in the lower (rectosigmoid) colon, the most common site for colorectal cancers. However, cancers also occur in areas of the colon too far from the anus to be accessible to sigmoidoscopes. Colonoscopy uses an instrument capable of examining the whole colon. Need for colonoscopy is controversial, and the procedure is not a routine study since it requires anesthesia, is more time-consuming, and more expensive to carry out. There is also a small risk of perforating the colon. It is done in patients determined to be at high risk for colon cancer, on the basis of their medical/family history, and the finding numbers of large polyps by sigmoidoscopy. A study carried out at the Lahey-Hitchcock Medical Center in Burlington, Massachusetts, reported in the January 2, 1997 issue of the New England Journal of Medicine, concludes that discovery of substantial numbers of even diminutive (less than 5 mm) or small (5-10 mm) polyps on sigmoidoscopy warrants performing a colonoscopy. After excluding those at higher risk because of previous history of colon cancers or polyps, or colon symptoms, these researchers found by colonoscopy that 29% of those with either small or diminutive polyps, and 57% of those with large (more than 11 mm) polyps had growths in regions of their colons inaccessible to sigmoidoscopy. These growths were mainly benign polyps, but were cancerous in from 6% (diminutive) to 29% (large polyp group) of those who had polyps visible on sigmoidoscopy. (Read, New Engl J Med 336:8, 1997)

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• Immunosuppression reduces the risk of rectal cancer! - An international research team from Canada, Germany and the UK examining the incidence of various gastrointestinal cancers among 73,076 men and women who had received heart or kidney transplants, found that there was a nearly three-fold reduction in the incidence of rectal cancer among them. The effect was greater in men than in women, and also was more pronounced among heart transplant cases. All transplant patients receive continuous immune-suppressing therapy to prevent organ rejection. The study had been set up to explore what was anticipated to be a reduced rate of stomach cancer because of suppression of the immune gastritis caused by infection with Helicobacter pylori. In fact, as reported in the January, 1997 issue of Clinical Cancer Research, the incidence of gastric cancer was absolutely unaffected, while that of colon cancer showed a small rise which might be expected with suppression of the immune response. (Stewart, Clin Cancer Res 3:51, 1997)