Since this cancer is highly curable in the early stages, several techniques for early detection are recommended. These apply to the general population but are especially recommended for people with first-degree relatives with colorectal cancer.
Screening for adenomas that may become carcinomas after 10 or 15 years should begin at age 40, with screening for cancer beginning at age 50. A digital rectal examination should be an annual routine for those over 40, along with testing stool for hidden blood. About 3 percent will have a positive hidden blood test, and anywhere from 20 to 50 percent of these will be positive for polyps or cancer (10 percent will have cancer, 20 to 30 percent will have adenomas). These tests have rates of 2 percent false positives and 30 percent false negatives. False negatives are high because colorectal cancers bleed intermittently and the test may be done between bleedings.
