Bridging radiotherapy before chimeric antigen receptor T cells for B-cell lymphomas: an ILROG multicenter study

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 (BCLs) who received Br-RT followed by CAR-T from 2018 to 2020 across 10 institutions. Br-RT toxicities were graded per Common Terminology Criteria for Adverse Events version 5.0, and cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) per American Society for Transplantation and Cellular Therapy Consensus Guidelines. One hundred seventy-two patients (168 large BCL) received Br-RT before axicabtagene ciloleucel (73%), tisagenlecleucel (24%), 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% and bridging systemic therapy to 35%. Among all patients, grade ≥3 Br-RT toxicity occurred in 2% (1 grade 5 toxicity), grade ≥3 CRS in 9%, and grade ≥3 ICANS in 24%. Median follow-up was 31.3 months. Two-year progression-free survival (PFS) and overall survival (OS) were 38% and 53%, respectively. On multivariable analysis, comprehensive Br-RT was associated with superior PFS (hazard ratio [HR], 0.38; P < .001) and OS (HR, 0.48; P = .011). Patients with lactate dehydrogenase (LDH) normalization after Br-RT (high pre-Br-RT LDH, normal post-Br-RT LDH) had superior PFS and OS compared with those with high post-Br-RT LDH and similar PFS and OS compared with those with normal baseline LDH. In this particularly high-risk cohort, Br-RT before CAR-T demonstrates an acceptable toxicity profile with favorable clinical outcomes compared with historical controls. Comprehensive Br-RT and LDH normalization after Br-RT may be associated with superior PFS and OS.