[Clinical significance of serum immunosuppressive substance as a marker of colorectal cancer].

Serum immunosuppressive substance (IS) was determined in 95 patients with colorectal cancer, 61 patients with benign gastrointestinal diseases and 32 healthy individuals. Serum carcinoembryonic antigen (CEA) was determined in 79 patients with colorectal cancer and 53 patients with benign gastrointestinal diseases. Serum IS in healthy individuals was 549.7 +/- 104.7 micrograms/ml, and 800 micrograms/ml (mean 'SD) was defined as cut-off value for positive serum IS. Cut-off values for serum CEA was defined as 2.5 ng/ml. The present study disclosed that determination of serum IS can not be used as a screening test for colorectal cancer, but combination assay of both serum IS and CEA improved the sensitivity of the test detecting colorectal cancer. Curative resection was possible in most patients with serum IS less than 1100 micrograms/ml, whereas resection was palliative or impossible in most patients with serum IS more than this value. Elevation of serum IS correlated closely with peritoneal dissemination, serosal invasion or extensive nodal metastasis. There was however, no correlation between the serum IS level and liver metastasis.