Monoclonal antibody detection of a circulating tumor-associated antigen. II. A longitudinal evaluation of patients with colorectal cancer.

An antigen identified by two monoclonal anti-colorectal cancer antibodies was studied in sera of 85 patients who had a resection of their primary colorectal cancer. Preoperative and postoperative serum samples and sera collected every 3 months for at least 1 year were included in this study. The levels of these antigens were compared to the carcinoembryonic antigen (CEA) levels. Sixty-six patients had at least one antigen elevated in the preoperative period. Malignancy recurred in 10 patients. In 8 of these the recurrence could have been predicted by the persistence or rise in antigen levels 3 to 18 months prior to the detection of the recurrence by current clinical methods. The data suggest that the assays for these antigens are valuable prognostic aids for making clinical therapeutic decisions and appropriately stratifying patients for clinical trials.