Clinicopathologic studies of immunologic fecal occult blood test for colorectal cancer

In our hospital, 83 patients with colorectal cancer underwent the immunologic fecal occult blood test (IFOBT). The positive rate for IFOBT in all patients was 87%. Colon cancers more proximal than the transverse colon were 100% positive. Carcinomas of the ulcerative type showed a significantly higher positive rate than those of the non-ulcerative type (94% vs 73%). Carcinomas penetrating the muscularis or beyond showed a significantly higher positive rate, of 96% (52/54 cases) compared to carcinomas confined to the mucosa or submucosa, which gave positive rates of 64% and 60%, respectively. In the investigation of the 7 patients with colorectal cancer who showed negative results on the IFOBT, IFOBT had been performed only once in of these patients. Accordingly, it was considered necessary to perform IFOBT more than once. The cancers in 5 of these 7 patients were found to be carcinomas confined to the mucosa. This result suggests the advisability of annual IFOBTs. It is also considered necessary to manage patients who show undefinable but possibly positive (+/-) results with caution.