Combining obinutuzumab with radiation for refractory DLBCL: Retrospective safety and efficacy analysis

Introduction Approximately 30% of patients with diffuse large B cell lymphoma (DLBCL) will develop relapsed or treatment refractory disease following primary chemotherapy. Patients unable to undergo aggressive chemotherapy and stem cell transplant (SCT) or 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 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 (CTCAE) v5.0 criteria. Kaplan Meier analysis was utilized to calculate progression free survival (PFS) and overall survival (OS). 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 seven patients had a complete response at the radiated site on first post-radiation imaging. The median PFS and OS were 30 months. Conclusion In this small cohort of treatment refractory DLBCL patients, 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.