Bridging Radiotherapy Prior to Chimeric Antigen Receptor T-Cells for B-Cell Lymphomas: An ILROG Multicenter Study.

Abstract

Despite the increasing utilization of bridging radiotherapy (Br-RT), its impact on chimeric antigen receptor T-cell therapy (CAR-T) efficacy and toxicity remains poorly characterized. We retrospectively reviewed patients with relapsed/refractory B-cell lymphomas (r/r BCL) who received Br-RT followed by CAR-T from 2018-2020 across 10 institutions. Br-RT toxicities were graded per CTCAE v5.0, and cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) per ASTCT Consensus Guidelines. 172 patients (168 large BCL, 3 mantle cell, 1 Burkitt) received Br-RT prior to axicabtagene ciloleucel (73%), tisagenlecleucel (23%), or brexucabtagene autoleucel (2%). At leukapheresis, most patients (74%) had advanced-stage disease and 39% had bulky disease measuring ≥10cm. Comprehensive Br-RT was administered to 39% (n=67) and bridging systemic therapy to 35% (n=60). Among all patients, grade ≥3 Br-RT toxicity occurred in 2% [one grade 5 toxicity], grade ≥3 CRS in 9%, and grade ≥3 ICANS in 24%. Median follow-up was 31.3 months. Two-year PFS and OS were 38% and 53%, respectively. On multivariable analysis, comprehensive Br-RT was associated with superior PFS (HR 0.38, p<0.001) and OS (HR 0.48, p=0.011). Patients with LDH normalization following Br-RT (high pre-Br-RT LDH, normal post-Br-RT LDH) had superior PFS and OS compared to those with high post-Br-RT LDH, and similar PFS and OS compared to those with normal baseline LDH. In this particularly high-risk cohort, Br-RT prior to CAR-T demonstrates an acceptable toxicity profile with favorable clinical outcomes when compared to historical controls. Comprehensive Br-RT and LDH normalization post-Br-RT may be associated with superior PFS and OS.