Role Of Radiation In Relapses In Relapsed/Refractory Diffuse Large B Cell Lymphoma (DLBCL) Post-Transplant

Abstract

Standard 2nd line treatment for relapsed/refractory (R/R) DLBCL is autologous stem cell transplant. ∼50% of patients still relapse and there is no standard salvage chemotherapy in this setting. There is also a limited role of radiation in patients with lymphoma relapses post-transplant. We explored the role of radiation as early salvage treatment in relapsed/refractory DLBCL patients post-transplant. Our hypothesis was that early salvage radiation therapy instead of early salvage chemotherapy may lead to shorter time to needing 2nd salvage treatment (i.e. relapse quicker due to delay in salvage systemic treatment). From an institutional database, patients with DLBCL who had an autologous hematopoietic stem cell transplant (auto-HSCT) during 2004 -2016 and subsequently relapsed were identified; post-relapse therapy dates and types were extracted from medical records. Clinical and pathologic characteristics were collected. The time from 1st line of relapse therapy to either 2nd line of therapy or death was computed; patients without 2nd line therapy or deaths were censored at the last contact. Of the 165 patients with relapsed/refractory DLBCL who received auto-HSCT and subsequently relapsed, 90 (55%) received salvage chemotherapy as their 1st line of relapse therapy and 13 (8%) received salvage radiation as their 1st line of relapse therapy. 7/13 (54%) of early salvage radiation patients had a complete response. The median time from 1st line salvage radiation to subsequent salvage (2nd line) or death was estimated to be 0.43 years, compared to a median time of 0.36 years from 1st salvage chemotherapy to subsequent salvage or death (log rank p = 0.95). 1 patient with 1st line salvage radiation was alive without subsequent salvage at 7.93 years. For the other 12 patients, the time from 1st salvage (which is radiation) to 2nd salvage treatment or death was 0.13-3.97 years, compared to a range of 0.02-6.48 years for the 81 patients with salvage chemotherapy as 1st line. While small number of patients received radiation as 1st salvage therapy, there were few durable responses with early salvage radiation. This suggests some post-transplant R/R DLBCL patients have oligometastatic sites of DLBCL relapse and can benefit from localized radiation early instead of salvage chemotherapy. Future studies are needed to understand the molecular subtypes of DLBCL that may benefit from early salvage radiation versus salvage chemotherapy.