Dose-Reduced Consolidation Radiation Therapy in Patients With Diffuse Large B-cell Lymphoma

This phase II study will evaluate whether a reduction in radiation dose and field size will maintain a high rate of local control while minimizing the risk of acute and late toxicity . Hypothesis: The radiation dose and treatment volume can be safely reduced from 30 Gy to 20 Gy while maintaining high rates of local control in patients who had a negative PET-CT scan following rituximab - containing chemotherapy.

Chemotherapy followed by consolidation radiation therapy (RT) is a recognized treatment paradigm for DLBCL. This was initially established based on the results of 2 randomized trials conducted in the 1980s-1990s. In these studies patients were treated with 30Gy after chemotherapy (ECOG study) or 40-55Gy (SWOG study). A British National Lymphoma Investigation study showed no difference in freedom from local progression, progression-free survival or overall survival in between patients receiving 30Gy and 40-45Gy. Additionally systemic therapy for DLBCL has significantly improved since these initial studies, with the addition of rituximab to standard chemotherapy. In a phase II study at Duke University patients with DLBCL NOS or primary mediastinal B-cell lymphoma were treated to 19.5-20Gy after achieving complete response to 4-6 cycles of chemotherapy containing rituximab. With a median follow-up of 43 months, there was only 1 local recurrence. The 5-year local control rate was 98%. Progression-free and overall survival at 5 years was 81% and 88%. Therefore, there is emerging evidence of long term favorable outcomes in localized DLBCL, while decreasing the risk of late effects by reducing the dose and volume of RT. All participants will receive 20Gy instead of 30-36Gy after completion of at least 3 cycles of rituximab with combination chemotherapy. Participants must have a negative post chemotherapy PET-CT to participate in this study.