Proposed treatment algorithm for management of PMBCL.⁺Observation alone without RT after therapies other than DA-EPOCH-R has not been studied in prospective trials to date. The ongoing IELSG-37 trial seeks to determine whether RT can safely be omitted in these patients. *RT alone or combined modality with auto-SCT are both reasonable approaches in this scenario and have not been compared in clinical trials. PD, progressive disease; SD, stable disease.