SALVAGE RADIOTHERAPY ASSOCIATES WITH DURABLE RESPONSE FOR A SUBSET OF PATIENTS WITH LIMITED STAGE REFRACTORY DIFFUSE LARGE B‐CELL LYMPHOMA

Abstract

Introduction. Despite favourable outcomes with chemoimmunotherapy for the majority of patients with diffuse large B-cell lymphoma (DLBCL), approximately one-third of patients experience relapsed or refractory disease portending poor prognosis. Patients ineligible for treatment intensification with salvage chemotherapy may be offered palliative chemotherapy or radiotherapy, and in the setting of single-site progression, salvage radiotherapy with curative intent. There remains a paucity of evidence for the latter with no randomised clinical trials or large series reported in the literature. The study was conducted to assess the outcomes of patients treated with salvage radiotherapy for limited stage relapsed / refractory DLBCL (rrDLBCL) at Monash Health, Australia, to determine its utility and inform future treatment algorithms. Methods. DLBCL cases (867 patients) diagnosed per WHO criteria at Monash Health, Melbourne, Australia, between 1996-2019 within the Haematology Database were analysed. Adult patients with rrDLBCL (including transformed indolent lymphoma) treated with salvage radiotherapy alone with curative intent were included in the study. Patients with inadequate clinical information or follow up data available or those in whom radiotherapy was administered as consolidation or clearly palliative intent were excluded. Results. From January 1996-December 2019, 18 eligible patients were identified for inclusion in the study (12 refractory and 6 relapsed). A further 14 patients were excluded due to radiotherapy for clearly palliative intent (n = 7), CNS relapse (n = 5), consolidation (n = 1) or prior indolent lymphoma (n = 1). Median age at radiotherapy commencement for the study population was 71 years (range 42-83). 11/18 had biopsy-proven refractory disease, a further 3/18 had inconclusive biopsy with high suspicion of active disease on imaging and remaining patients were treated on basis of high clinical suspicion from PET imaging with sites not amenable to biopsy. Median radiotherapy dose was 42 Gy (range 10-50). After a median follow up of 14 months (range 1-64), 11/18 patients progressed (Fig. 1) after a median of 2 months (range 0-20). 7/18 (39%) patients remain in an ongoing remission without any progression events after a median of 29 months (range 13-64). Of the primary refractory subset, 4/12 (33%) remain free from progression with a median follow up of 32 months (range 13-64). Conclusion. Salvage radiotherapy with curative intent confers meaningful disease control for a subset of patients with limited stage rrDLBCL. Despite the small sample size and retrospective nature of the study, we conclude salvage radiotherapy should be considered a treatment option for patients ineligible for salvage chemotherapy in cases of single site rrDLBCL. These findings warrant further clinical investigation.