RADIOLABELED-ANTIBODY THERAPY OF B-CELL LYMPHOMA WITH AUTOLOGOUS BONE-MARROW SUPPORT

Background. Radiolabeled monoclonal antibodies recognizing B-lymphocyte surface antigens represent a potentially effective new therapy for lymphomas. We assessed the biodistribution, toxicity, and efficacy of anti-CD20 (B1 and 1F5) and anti-CD37 (MB-1) antibodies labeled with iodine-131 in 43 patients with B-cell lymphoma in relapse. Methods. Sequential biodistribution studies were performed with escalating doses of antibody (0.5, 2.5, and 10 mg per kilogram of body weight) trace-labeled with 5 to 10 mCi of I-131. The doses of radiation absorbed by tumors and normal organs were estimated by serial gamma-camera imaging and tumor biopsies. Patients whose tumors were estimated to receive greater doses of radiation than the liver, lungs, or kidneys (i.e., patients with a favorable biodistribution) were eligible for therapeutic infusion of I-131-labeled antibodies according to a phase 1 dose-escalation protocol. Results. Twenty-four patients had a favorable biodistribution, and 19 received therapeutic infusions of 234 to 777 mCi of I-131-labeled antibodies (58 to 1168 mg) followed by autologous marrow reinfusion, resulting in complete remission in 16, a partial response in 2, and a minor response (25 to 50 percent regression of tumor) in 1. Nine patients have remained in continuous complete remission for 3 to 53 months. Toxic effects included myelosuppression, nausea, infections, and two episodes of cardiopulmonary toxicity, and were moderate in patients treated with doses of I-131-labeled antibodies that delivered less than 27.25 Gy to normal organs. Conclusions. High-dose radioimmunotherapy with I-131-labeled antibodies is associated with a high response rate in patients with B-cell lymphoma in whom antibody biodistribution is favorable.