The genetics, epidemiology, and early detection of gastrointestinal cancers

Current recommendations for screening large populations for colorectal neoplasia have been promulgated by a number of researchers and authorities who generally agree that ongoing screening is justifiable in high-risk groups but not yet in average-risk groups. Nonetheless, it is thought to be justifiable to provide screening for average-risk individuals upon request. Choice of tools for screening remains under discussion. Colonoscopy is generally agreed to be justifiable in those patients with the highest risk, ie, members of families with a clear inherited tendency to develop colorectal cancer or those with a personal history of colorectal neoplasia. There is currently no agreement concerning the recommended tools for those with a weaker family history (one or two affected relatives), but regular fecal occult blood testing with occasional limited endoscopic examination of the bowel is usually favored. The new immunochemical-based occult blood tests show great promise for improved sensitivity and specificity. The evidence of the association between Helicobacter pylori gastritis and gastric cancer has been strengthened by three studies that show that patients with gastric cancer are more likely to have had infection in the years (up to 20) prior to diagnosis. The relative risk for cancer when infected with H. pylori is 3.6 to 6, but many H. pylori-positive individuals do not develop gastric cancer and additional factors must be operative. Probably the most exciting development for gastroenterology in 1991 is the identification of the gene on chromosome 5, designated APC, which is responsible for familial adenomatous polyposis.(ABSTRACT TRUNCATED AT 250 WORDS)