Circulating immune complexes in patients following clinically curative resection of colorectal cancer.

Sixty-nine patients have been followed prospectively after curative resection of Dukes-Kirklin B-2 or C colorectal cancer. Serial plasma samples were studied in selected patients to determine changes in circulating immune complex concentrations (CIC) following primary tumor resection, and to compare serial plasma CIC and carcinoembryonic antigen (CEA) levels. CIC was determined in an average of seven serial samples per patient by inhibition of antibody-dependent cell-mediated cytotoxicity (ADCC). CEA assays were performed by the Hanson Z-gel method. Two distinct patterns of serial CIC have emerged. In seven patients with no known tumor recurrences, serial CEA levels and CIC oscillated regularly and were inversely related. In seven of eight patients whose tumors recurred, both CEA and CIC rose together. In three patients with elevated plasma CEA levels due to inflammatory bowel disease, serial Ag-Ab complex concentrations did not vary, nor did separated Ag or Ab fractions inhibit ADCC. These data suggest that, in patients following curative resection of colorectal cancer, serial changes in circulating immune complexes may discriminate between transient CEA elevations which occur despite no known tumor recurrence and tumor recurrence which is beyond the capacity of adequate host antitumor defense.