Role of radiation therapy in primary mediastinal large B-cell lymphoma in rituximab era: A US population-based analysis

The use of radiation (RT) in primary mediastinal large B-cell lymphoma (PMBCL) may predispose young patients to the risk of cardiopulmonary toxicities and secondary malignancies. We used Surveillance, Epidemiology and End Results (SEER) 18 database to compare the overall survival (OS) differences among adult patients treated with and without RT after rituximab approval in the US. Multivariate analyses were performed using Cox proportional hazards regression to compare OS based on the use of RT while adjusting for age, year of diagnosis, race, stage and gender. PMBCL patients (n = 258), who received RT (48%), were similar in terms of age, gender, race, and stage at diagnosis to patients who did not receive RT. The five year OS was similar between patients treated with versus without RT (82.5% vs. 78.6%, P = 0.47). In a multivariate analysis, the use of RT did not influence OS in the rituximab era (HR 0.83; 95% CI 0.43-1.59; P = 0.56). Rituximab may reduce the benefit of RT in select patients such as those who achieve a metabolic complete remission at the end of chemotherapy.