Is Radiotherapy Adequate Treatment for Patients not in Complete Metabolic Response after First-Line Chemotherapy for DLBCL?

Abstract

Failure to achieve complete metabolic response (CMR) on 18-FDG PET/CT at the end of chemotherapy (CT) in diffuse large B cell lymphoma (DLBCL) is associated with poor prognosis. Patients (pts) are usually considered for salvage CT and autologous stem cell transplant if fit. However salvage often fails and is not suitable for a substantial proportion of pts. A subset of these pts have localised uptake that can be treated with radiotherapy (RT) but the efficacy of RT in this situation is not established. This study aims to assess the efficacy of salvage RT after incomplete response to first line CT and identify factors that may predict its efficacy. We performed a retrospective review of DLBCL pts who had residual FDG uptake on PET/CT after first line CT and subsequently received RT. Eligibility included: treatment with curative intent, RCHOP or similar, post-CT PET/CT Deauville score (DS) 4 - 5, RT ≥30Gy within 8 weeks. End points included: relapse rate, pattern of relapse, response to RT and overall survival (OS). We included 44 pts treated March 2011-August 2018 with median follow up (FU) of 29.3 months (1.6-90.8). Table 1 shows pt, disease and treatment characteristics. 45.5% were stage 3-4. 88.7% received RCHOP/RminiCHOP with median of 6 cycles. DS was 4 and 5 in 77.3% and 22.7%. During FU 14 (31.8%) pts relapsed/progressed. 10 (71.4%) relapsed outside the RT volume, 1 (7.1%) inside and 3 (21.4%) relapsed in both. Progression occurred relatively early with a median time from RT of 4.0 months (0.8-51). Of those who relapsed, 6 received salvage CT and 3 are alive with median FU of 50.8 months (26.9-90.7). 13 pts died, 11 of lymphoma and 2 of unrelated causes. Median OS is 75 months (1.6-90.8). PET/CT scans were performed after RT in 40/44 (90.9%) of pts. Half achieved CMR, 10 had DS 4 and 10 DS 5. The risk of relapse was related to the post RT PET status. 9/10 (90%) of pts with DS5 relapsed compared to 1/10 (10%) with DS4 and 4/20 (20%) of pts with CMR. Relapse risk was also related to the pre RT DS. Relapse occurred in 5/10 (50%) pts with DS 5 compared to 9/34 (26.5%) with DS 4. There was no difference in relapse rate according to RT dose (30/30.6 vs ≥36Gy). RT seems to be an adequate treatment for a substantial proportion of pts not achieving CMR following initial CT with more than half remaining in long term remission. Pts with post CT DS 4 had a better outcome after RT.Abstract 139; Table 1Patient and treatment characteristics Male Femalen (%) 22 (50) 22 (50)Median Age /years (range)65.5 (21-89)Histopathology Germinal centre (GC) Non GC THRLB-CL PMBCL NOS16 (36.3) 10 (22.7) 2 (4.5) 6 (13.6) 10 (22.7)Stage 1 2 3-44 (9.1) 20 (45.5) 20 (45.5)IPI 0-1 2 3 4-516 (36.4) 11 (25) 9 (20.5) 8 (18.2)Median no of cycles (range) R miniCHOP RCHOP/RCEOP RGCVP/RCVP COPADM-R6 (3-8) 9 (20.5) 31 (70.5) 3 (6.8) 1 (2.3)End of CT DS 4 534 (77.3) 10 (22.7)RT dose (Gy) 30/30.6 36 4017 (38.6) 18 (40.9) 9 (20.5) Open table in a new tab