Improved Progression-Free Survival for Bulky and Non-Bulky Advanced Stage Diffuse Large B-Cell Lymphoma with Consolidative Radiation Therapy: A Bi-Institutional Analysis

Background: The role of consolidative radiation therapy (RT) for advanced stage diffuse large B-cell lymphoma (DLBCL) is not fully established. Retrospective data provide evidence for the use of consolidative RT in stage III-IV DLBCL and emerging data from randomized studies address the role of RT in bulky disease for these patients. Methods: Patient with stage III-IV DLBCL treated at two institutions who achieved clinical complete response to systemic therapy were included. Kaplan-Meier analysis was performed to determine the impact of consolidative RT. Univariate and multivariable analyses were performed using a Cox proportional hazards model. Results: One hundred eighty-eight patients received systemic therapy consisting of R-CHOP (79%), another Rituximab-based regimen (9%), or chemotherapy alone (12%). Clinical response was assessed using conventional CT or PET-CT. Sixty-eight patients (36%) received consolidative RT (median dose 30 Gy). Consolidative RT conferred a 36.7% absolute benefit in five-year progression-free survival (85.9% vs. 49.2%, log rank p < 0.0001), and a 14.5% absolute benefit in five-year overall survival (87.4% vs. 72.9%, log rank p = 0.0134). On multivariable analysis, consolidative RT was associated with improved PFS (HR 0.23, 95% CI 0.10-0.52, p < 0.001). Patients receiving consolidative RT demonstrated significantly improved PFS for tumors measuring both <5 cm (log rank p = 0.0454) and ³5 cm (log rank p = 0.0003). Conclusions: For patients with stage III-IV DLBCL who achieve clinical complete response after systemic therapy, consolidative RT improves PFS for all patients, including those with non-bulky disease. This benefit persists in the setting of rituximab-based systemic therapy.