Prospects of radioimmunotherapy in epithelial ovarian cancer: Results with iodine-131-labeled murine and humanized MN-14 anti-carcinoembryonic antigen monoclonal antibodies

Objectives. Epithelial ovarian cancer (EOC) is known to produce carcinoembryonic antigen (CEA), and the plasma CEA level is frequently elevated in patients with advanced stage and bulk of tumor. This study reports the results of a phase I therapy trial with intravenously administered I-131-MN-14 anti-CEA monoclonal antibody (MAb) in patients with EOC. Methods. Fourteen patients with advanced refractory EOC were given escalating intravenous doses (two received 30 mCi/m(2), six 40 mCi/m(2), and six 50 mCi/m(2)) of I-131-MN-14 IgG. All patients received a diagnostic study with 8 mCi (0.6 mg) of I-131-MN-14 IgG 1 week prior to their therapy infusion. Tumor targeting was assessed by external scintigraphy, toxicity according to the Radiation Therapy Oncology Group criteria, and therapy responses by CT and serum CA-125. Results. The MAb scan was positive in all 14 treated patients. Myelosuppression was the only observed treatment-related toxicity. Dose-limiting toxicity, defined as grade 4 leukopenia or thrombocytopenia of any duration, or grade 3 leukopenia or thrombocytopenia of > 2 weeks, was not seen at the 30 or 40 mCi/m(2) dose levels. However, 2 of 6 patients treated at 50 mCi/m(2) had a grade 4 thrombocytopenia or a grade 3 thrombocytopenia lasting 18 days. Of the 14 patients, 1 with diffuse peritoneal implants of less than or equal to 2 cm had a complete clinical remission by CT and CA-125 for 8 months, following an initial partial remission for 10 months, both at the 40 mCi/m(2) dose level, Another patient had a mixed response for 1 month. Conclusion. MN-14 anti-CEA MAb is a suitable agent for tumor targeting and may have a therapeutic potential in patients with chemotherapy-refractive EOC, especially those with minimal disease. (C) 1997 Academic Press.