Results of screening for colorectal cancer.

Screening for colorectal cancer and its precursors was performed from '68 to '78 within the framework of a multiphasic cancer detection program on 35,700 "healthy" individuals of both sexes in the "high-risk" age groups. Fecal occult blood as determined by the benzidine test after diet was positive in 3,676 individuals (10.3%). Out of this group, 2,599 subjects were submitted to g.i. consultation and proctosigmoidoscopy, as well as 567 of the occult blood negative group selected on the basis of various clinical signs and symptoms. The lesions detected were 153 neoplastic polyps and 21 cancers, mostly in the Dukes A and B stages. Among the most significant results are the high compliance (70%) to proctosigmoidoscopy, the low sensibility (51%) and specificity (18%) of the benzidine test for occult blood, which makes it obsolete as a screening procedure, the increased (50%) diagnostic yield obtained by flexible sigmoidoscopy and the relevance of clinical signs and symptoms as selection parameters for further diagnostic work up.