Reduction in colorectal cancer mortality related to annual fecal occult blood screening--13 year follow-up of 46,000 subjects.

46,551 participants 50 to 80 years of age were recruited from among volunteers for the American Cancer Socie~, fraternal, veterans, and employee groups in Minnesota between 1975 and 1977. Excluded from the study were persons with history of colorectal cancer, familial polyposis, or chronic ulcerative colitis, and persons who were bedridden or otherwise disabled. After stratification by age, sex, and place of residence, subjects were randomized to one of three groups: annual screening, biennial screening, or a control group.2