Role of consolidative radiation therapy for patients with mediastinal diffuse large B-cell lymphoma in the rituximab era

Background: The most common subtype of aggressive non-Hodgkin Lymphomas is diffuse large B-cell lymphoma (DLBCL). Mediastinal DLBCL is a distinct entity with unique clinical, pathologic, and genetic features and accepted as a subtype of DLBCL. The aim of this study is to evaluate the patients treated with consolidative radiotherapy (RT) after rituximab-containing chemotherapy for mediastinal DLBCL regarding treatment outcomes and relapse patterns. Material and Methods: Forty-two patients with the diagnosis of mediastinal DLBCL who were treated at the Ege University Hospital between January 2008 and December 2014 were evaluated. All patients received 2-10 cycles of rituximab-containing chemotherapy schedule (mostly CHOP). RT was delivered to a total dose of 30.6-45 Gy with 1.8 Gy daily fractions in 4-5 weeks. The irradiation fields were designed by using involved lymphatic site technique. Results: The median age at diagnosis was 53 years (range, 18-85 years). Ann Arbor clinical stage at diagnosis was as follows: 8 patients (19%) at Stage I, 20 patients (47.6%) at Stage II, 7 patients (16.7%) at Stage III, and 7 patients (16.7%) at Stage IV. The median follow-up period was 47 months (range, 7-96 months). Complete response was obtained in 27 patients (64.3%), partial response was obtained in 14 patients (33.3%) across all stages. Estimated 5-year overall survival (OS) and progression-free survival (PFS) rates were, respectively, 84% and 77% for all patients, 100% and 92% for the patients without residual disease after chemotherapy. Conclusion: The response to chemotherapy is the most important factor affecting both OS and PFS. The role of consolidative RT is not clear in the rituximab era due to the lack of phase III trial. However, available literature shows that consolidative RT may still have a role in mediastinal DBLCLs.