Outcomes of limited stage primary bone diffuse large B-cell lymphoma in the rituximab era: a multicenter, retrospective study.

Primary bone diffuse large B-cell lymphoma is a rare variant of extranodal non-Hodgkin lymphoma historically treated with induction chemotherapy followed by consolidative radiation therapy (RT). It remains unknown whether RT confers additional benefit following rituximab-based chemoimmunotherapy (CIT) induction in patients with limited stage disease. We conducted a multicenter, retrospective analysis of patients treated between 2005 and 2019 using rituximab-based CIT regimens with or without consolidative RT to discern whether consolidative RT adds benefit in patients with stage I-II disease that could be encompassed in one radiation field. A total of 112 patients were included: 78 received CIT and radiation (RT group), and 34 received CIT alone (no RT group). The overall survival at 10 years was 77.9% in the RT group and 89.0% in the no RT group (P=0.42). The relapse-free survival at 10 years was 73.5% in the RT group and 80.3% in the no RT group (P=0.88). Neither improved overall survival nor relapse-free survival was associated with the addition of consolidative RT. Subgroup analysis of patients only achieving a partial response after CIT suggests that these patients may benefit from consolidative RT.