ABSTRACT
Colorectal cancer is the fourth most common nonskin cancer worldwide with an estimated 678,000 cases and 394,000 deaths in 1985. However, it is less common in developing countries, where stomach cancer currently poses a greater burden. The age-incidence curve for both colon and rectal cancer is typical of epithelial tumors and increases approximately as the fifth to sixth power of age. Studies of migrant populations support lifestyle as a major determinant of colorectal cancer risk. The possibility that estrogens might play a role in colon cancer has been suggested by a number of studies. Ulcerative colitis has long been known to predispose a person to colon cancer with a risk on the order of 10-fold and a cumulative lifetime incidence of about 5%. More direct evidence for the adenoma-carcinoma sequence comes from the finding of contiguous lesions. Endoscopic screening has a different goal than fecal occult blood tests, which is primarily an early detection measure.
