Feasibility and toxicity of concomitant radio/immunotherapy with MabThera (Rituximab®) for patients with non-Hodkin's Lymphoma: results of a prospective phase I/II study.

Purpose: Non-Hodgkin's lymphomas (NHL) have a high radio- and chemosensitivity. Although initially responsive, approximately 50% of low grade B-cell lymphomas relapse after 10-15 years. Besides chemo- and radiotherapy, rituximab, a mouse/human chimeric antibody targeting CD20 antigen on the surface of B-cell lymphoma cells, is another treatment approach. In vitro data showed potentiation of radiation-induced apoptosis by addition of rituximab. The purpose of this study was to evaluate the feasibility and toxicity of radiotherapy with concomitant application of rituximab in NHL patients.

Patients And Methods: A total of 21 patients with B-cell lymphoma (stage I: n = 11; II: n = 5; III: n = 1; IV: n = 4) were included in this study, treated with radiotherapy of 30-40 Gy and weekly application of rituximab (375 mg/m²). Nine patients had R-CHOP chemotherapy previously, 1 patient leuceran chemotherapy, and 2 patients an initial treatment with 6 cycles of rituximab. Mean time of follow-up was 41.7 months.

Results: No grade 4 toxicity or treatment-related death was observed. In 1 patient, rituximab application had to be stopped after 3 cycles due to radiation-induced side effects. No late toxicities were reported. All patients were in complete remission after treatment. Progression or relapse was observed in 6 patients (28%); the mean time to progression was 27 months. The mean overall survival (OS) was 53 months.

Conclusion: Combined radio/immunotherapy is feasible and safe. Treatment was well tolerated, no late toxicities were observed, and treatment outcome is promising. Randomized trials are necessary to clarify the benefit of this treatment approach and its applicability.