Combining Obinutuzumab With Radiation for Refractory DLBCL: Retrospective Safety and Efficacy Analysis

Abstract

Purpose: Approximately 30% of patients with diffuse large B cell lymphoma (DLBCL) will develop relapsed or treatment-refractory disease after primary chemotherapy. Patients unable to undergo aggressive chemotherapy and stem cell transplant or chimeric antigen receptor T-cell (CAR T-cell) therapy have limited treatment options. Here, we investigated the safety and efficacy of combining obinutuzumab with cytoreductive radiation to all areas of disease in patients with relapsed DLBCL. Methods and Materials: A retrospective review of patients with treatment refractory DLBCL was performed. All patients were treated with external beam radiation to all sites of refractory disease with concurrent and adjuvant obinutuzumab. Toxicities were evaluated based on Common Terminology Criteria for Adverse Events v5.0 criteria. Kaplan-Meier analysis was used to calculate progression-free survival and overall survival. Results: Between 2016 and 2022, 7 patients with refractory DLBCL were treated with concurrent radiation and obinutuzumab. No grade 3 or greater treatment-related toxicity was observed. Four of the 7 patients had a complete response at the radiated site on first postradiation imaging. The median progression-free survival and overall survival were 30 months. Conclusions: In this small cohort of treatment-refractory patients with DLBCL, the combination of radiation and obinutuzumab was well tolerated without excessive treatment-related toxicity. The combination resulted in durable disease control with a prolonged overall survival without additional treatment in a subset of patients.