The CancerWeb Report, What's New In Cancer: September, 1996
Colorectal Cancer

• The role of screening and surveillance - The topic of screening and surveillance for colorectal cancer was discussed in a very readable review in the June, 1996 issue of the Journal of Investigative Medicine. Between 80 and 85% of colorectal cancers are sporadic. The remaining 15-20% are hereditary, falling in the categories of hereditary nonpolyposis colon cancer, familial adenomatous polyposis (inherited tendency to polyps in the colon), and Gardner's and Turcot's syndromes. What is now known is that the more common sporadic cancers also start as polyps, protruding outgrowths of the colon wall, which grow and years later may become malignant. It is those polyps which grow to a large size (over about « inch) that are most prone to becoming malignant. Polyps are rare below the age of 50, occurring in only 5-10% of the population, but the incidence increases sharply after that. This is one reason why the procedure of sigmoidoscopy is recommended for those over this age. Use of sigmoidoscopy reduced mortality by 59% and 79% in two studies. Tests for blood in the stools should start at age 40, and although these tests are not highly reliable because not all early colon cancers bleed, five studies in different countries showed that the tests increase by between 5 and 100% the number of cancers found at an early operable stage. Colonoscopy, a complete examination of the colon under anesthesia by a longer viewing instrument than that used for sigmoidoscopy, is only recommended for those known to have a tendency to form polyps whether by heredity or as shown by previous findings of such polyps during sigmoidoscopy, those with a history of successfully operated colon cancer, and those with chronic ulcerative colitis of more than 8 years duration. Newer tests are being developed based on various genetic features and mutations, and it may eventually be feasible to measure such special features in cells shed from the colon and found in the stools. (Westergaard, J Investigative Med 44:216, 1996)