A multi-institutional analysis of diffuse large B-cell lymphoma (DLBCL) treated with consolidative radiotherapy and the impact of cell-of-origin on outcomes.

Background Patients with diffuse large B-cell lymphoma (DLBCL) with bulky disease and/or those who fail to achieve complete response benefit from the addition of radiotherapy (RT). We aim to review the outcome, as well as determine the impact of cell-of-origin, on patients undergoing consolidative RT. Patients and methods Patients with DLBCL treated with radical intent consolidative RT were included. Clinical, pathological and treatment characteristics were extracted from electronic medical records. Survival outcomes and factors that predict for disease-free survival (DFS) were analysed. Results Seventy-four patients were included in this analysis. The median follow up was 3 years (0.7-16 years). Fifty-eight percent of patients had stage I-II disease, and 61% received at least 6 cycles of chemotherapy. Cell-of-origin was discernible in 60% of patients, and approximately half were classified as Germinal centre origin. The 5-year overall survival (OS) of this group was excellent at 92% (median survival not reached). The 5-year DFS was 73% (95% CI 57-83%). Seven percent (n = 5) of patients experienced local recurrence at a median time of 6 months. Failure to achieve complete response post RT and/or initial bulky disease are significant predictors of inferior DFS. There was no association between cell-of-origin and DFS or OS. Conclusions The outcome of patients who received radiotherapy as consolidation is excellent. Patients who fail to achieve complete response after radiotherapy had poorer outcomes. Despite using radiotherapy, presence of bulky disease remains a significant predictor of disease recurrence. We did not find any association of poorer outcomes, with regards to cell-of-origin, in the use of consolidative RT.