Radiation therapy

Primary mediastinal B-cell lymphoma in adults is currently and primarily treated with a combination of chemotherapy and the monoclonal antibody rituximab (chemoimmunotherapy). Following chemoimmunotherapy, adult patients receive radiation therapy if they have a residual abnormality that is concerning for active tumor. Although most patients with primary mediastinal B-cell lymphoma demonstrate residual tissue abnormalities at the end of chemoimmunotherapy, this does not definitively indicate active tumor. Positron emission tomography–computed tomography (PET-CT) scans are useful to differentiate active tumor from fibrotic tissue in patients treated for mediastinal lymphoma.

Although lymphoma is responsive to radiation therapy, the role of radiation therapy has not been clearly determined in the up-front setting of primary mediastinal B-cell lymphoma. The results from a prospective randomized trial in adults with primary mediastinal B-cell lymphoma who were treated with R-CHOP with or without radiation therapy demonstrated that patients assigned to radiation therapy had a superior EFS, with no differences in PFS and OS.[97] The role of radiation therapy is less clear in the setting of more dose-intensive regimens that contain rituximab, such as DA-EPOCH-R.

Pediatric data are limited on the use of radiation therapy in the initial management of primary mediastinal B-cell lymphoma. Prospective pediatric studies that did not include radiation therapy have been conducted. In a retrospective analysis on the use of DA-EPOCH-R, radiation therapy was only administered in a small subset of pediatric patients (4 of 36 patients), highlighting the limited use of radiation therapy among pediatric patients treated outside of clinical trials.[94] The management of primary mediastinal B-cell lymphoma in pediatric patients, as with other childhood cancers, requires considering the efficacy and the long-term toxicity of the treatment. In particular, the potential for cardiac and pulmonary toxicities and secondary malignancies must be considered. More intensive chemotherapy regimens may allow for omitting radiation therapy but may also increase cardiac toxicity.