We aimed to analyze the safety and efficacy of a radiation bridging regimen with or without chemotherapy compared with chemotherapy alone prior to CAR T-cell treatment for relapsed/refractory aggressive B-cell lymphoma (r/r ABL).

In this study, 45 out of 105 patients enrolled in CD19/22 CAR T-cell "cocktail" clinical trial were excluded, including 34 patients without bridging treatment. Total 60 patients receiving CAR T-cell therapies with bridging regimens as chemotherapy alone (C-CAR-T group, n = 31), and radiotherapy with or without chemotherapy (R-CAR-T group, n = 29) between February 2017 and October 2020 were retrospectively analyzed.

No significant toxicities were identified in the R-CAR-T group, and no patients in either group experienced CAR-T-related deaths. However, the R-CAR-T group showed a lower incidence of cytokine release syndrome (CRS) of grade ≥ 3 relative to the C-CAR-T group (0% vs 19.4%, P = 0.036). The incidence of neurological toxicity was 9.9% and 6.9% in the C-CAR-T group and R-CAR-T group, respectively (P = 0.697). The R-CAR-T group achieved a higher overall response rate (ORR) at the day 30 assessment (82.8% vs 45.2%, P = 0.0025). Further analyzing the outcomes, the R-CAR-T group presented a better 1-year progression-free survival (PFS) rate than the C-CAR-T group (46.9% vs 22.6%, P = 0.0356). Intriguingly, the bridging radiation regimen extremely improved the 6-month PFS (50.8% vs 16. 7%, P = 0.0369) and 1-year overall survival (OS) (56.3% vs 33.3%, P = 0.0236) rates in patients with bulky disease. The study also found that conducting radiotherapy as a bridging regimen was an independent factor that predicted better PFS (HR: 0.534, 95% CI: 0.289-0.987, P = 0.045).

Our results provide and strengthen novel insights that the use of radiotherapy as a bridging strategy was demonstrated to reduce the incidence of severe CRS and improve the PFS of patients. In subgroup analysis, it was confirmed that radiotherapy can improve PFS and OS in patients with bulky disease. These findings open new avenues to improve the efficacy and safety of CAR T-cell therapy.