Role of radiation therapy in primary breast diffuse large B-cell lymphoma in the Rituximab era: a SEER database analysis

Primary breast diffuse large B-cell lymphoma (PB-DLBCL) is an uncommon extranodal non-Hodgkin's lymphoma (NHL), which was traditionally treated with anthracycline-containing regimens followed by consolidative radiation therapy (RT) to add therapeutic benefits. The introduction of anti-CD20 antibody rituximab for the treatment of B-cell NHLs has significantly improved the clinical outcome of these malignant diseases. It is unclear, however, whether consolidative RT could still add therapeutic benefits for PB-DLBCL patients treated with rituximab. To answer this important question, we used the Surveillance, Epidemiology, and End Results (SEER) database to evaluate the impact of RT on the clinical outcomes of PB-DLBCL patients in the rituximab era. Information on patient age, year of diagnosis, stage, race, laterality, and RT status for PB-DLBCL patients diagnosed between 2001 and 2014 were extracted. Kaplan-Meier survival curves were plotted, and log-rank test was used to compare the potential survival difference. Multivariate analysis using Cox proportional hazards model was employed to determine the impact of RT and other factors such as age, race, tumor laterality, stage, and year of diagnosis on survival. Among the 386 patients identified, the median follow-up time was 45 months (range, 0-167 months); the median age was 64 years (range, 19-93 years); 33.9% of the patients were younger than 60 years of age; 69.9% of the patients were stage I; 79.0% were white; 51.8% received RT. The 5-year OS and cause-specific survival (CSS) for the whole cohort were 72.3% and 82.5%, respectively. The 5-year OS was significantly superior for patients who received RT compared to those who did not receive RT (78.1% vs. 66.0%, P = 0.031). In multivariable analysis, RT remained significantly associated with improved OS (P = 0.026). In summary, our study suggests that RT still adds significant therapeutic benefits for patients with PB-DLCBL in the rituximab era.