2790 - Risk-Adapted Consolidative Radiotherapy in Rituximab-Treated Diffuse Large B-Cell Lymphoma: A Single-Institution Cohort

Purpose/Objective(s): To determine whether consolidative radiotherapy (RT) is associated with improved relapse-free survival (RFS) after rituximab-containing frontline therapy, focusing on stage-specific benefit.

Materials/Methods: Adults with systemic DLBCL treated with rituximab-containing frontline immunochemotherapy (2016–2020) were retrospectively reviewed; primary CNS lymphoma was excluded. Primary endpoint was RFS, defined as time from diagnosis to documented progression date, censored at death. RT status was abstracted from the medical record. RFS was estimated by Kaplan–Meier and compared by log-rank; Cox models evaluated univariable and adjusted associations (stage, IPI, B symptoms, ECOG).

Results: Among 379 rituximab-treated patients, 274 had post–frontline therapy radiotherapy status documented (RT n=162; no RT n=112; median age 56; stage I–II 54%), the strongest association was observed in limited-stage disease: stage I–II 2-year RFS was 93.7% with RT versus 80.4% without RT (HR 0.34, p=0.045). In contrast, no significant difference was seen in stage III–IV (HR 0.92, p=0.815). In the overall cohort, relapse occurred in 23 RT patients (14.2%) versus 29 without RT (25.9%; Fisher p=0.019), and 2-year RFS was 87.1% with RT versus 74.5% without RT (log-rank p=0.0036; univariable HR 0.44, 95% CI 0.25–0.78). Among complete responders, relapse was 6.7% with RT versus 19.1% without RT (p=0.015). After multivariable adjustment, RT demonstrated a nonsignificant trend toward improved RFS (HR 0.66, p=0.196).

Conclusion: In rituximab-treated DLBCL, consolidative RT was associated with fewer relapses and improved RFS, with the clearest signal in limited-stage disease and among complete responders. The attenuation after adjustment highlights potential selection bias and supports validation using prospective or propensity-adjusted analyses to refine RT selection.