Serum levels of tumor markers and presence of human antimouse antibodies: implications for diagnosis and treatment with radiolabeled monoclonal antibodies.

Our study is based on 100 radioimmunodetections and five immunotherapies in 84 patients with advanced carcinomas. We used a monoclonal anti-CEA F(ab')2 and anti-CA 19.9 F(ab')2 antibody "cocktail" in 75% of the cases and monoclonal anti-alpha FP, anti-beta HCG, and OC 125 F(ab')2 antibodies in the other cases. In all cases, we determined plasma tumor marker levels immediately before imaging. The positivity of the scans was analyzed in relation to the levels of plasma markers. We found that the imaging should be planned only in the cases in which marker levels exceed minimum thresholds. We developed an enzymoimmunologic assay to measure antimouse antibodies. We found that patients who received monoclonal antibodies developed in the mouse produce such antimouse antibodies. The kinetics of this production are analyzed to define the optimal sequence for more than one administration of monoclonal antibodies.