Is autologous transplantation (autoHCT) in relapsed diffuse large B-cell lymphoma (DLBCL) patients achieving only a PET/CT positive partial remission (PR) appropriate in the CAR-T cell era?

Abstract

8000 Background: In relapsed, chemosensitive DLBCL patients (pts), autoHCT consolidation is a standard therapy option. With the approval of anti-CD19 CAR T-cells in 2017, relapsed DLBCL pts with residual PET/CT avid disease after salvage therapies are increasingly being offered CAR T-cells in lieu of autoHCT. According to Center for International Blood and Marrow Transplant Research (CIBMTR) data in 2018, the number of autoHCT for DLBCL in the U.S. decreased by ~45% from prior years, likely due to application of CAR T-cells for both chemorefractory DLBCL and chemosensitive DLBCL pts not achieving a complete remission. Using the CIBMTR database, we report outcomes of autoHCT in relapsed chemosensitive DLBCL pts achieving only a PET/CT+ PR prior to HCT. Methods: 249 relapsed DLBCL pts undergoing an autoHCT from 2003-13 with a PET/CT+ PR prior to transplant were identified. The study cohort was divided into two groups: (a) early chemo-immunotherapy failure (ECF) defined as pts with primary refractory disease (PRefD) or relapse within 12 months of diagnosis, (b) late chemoimmunotherapy failure (LCF) defined as pts relapsing ≥12 months. Primary outcome was overall survival (OS). Secondary outcomes included progression-free survival (PFS) and relapse. Results: 182 pts had ECF and 67 pts had LCF. The median age of ECF pts was 57 years versus (vs) 63 years for LCF (p < 0.01). ECF pts more frequently had stage III-IV at diagnosis (74% vs 54%, p = < 0.01). 79% of ECF pts had PRefD. The most common conditioning regimen was BEAM in both cohorts. The adjusted 5-year probabilities for PFS and OS (ECF vs LCF) was not different between the 2 cohorts: 41% vs 41% (p = 0.93) and 51% vs 63% (p = 0.09), respectively. Cumulative incidence of relapse at 5 years in similar order was 48% vs 57%, p = 0.27. On multivariate analysis compared to the LCF, pts with ECF had an increased risk of death (HR = 1.61, 95%CI 1.05-2.46, p = 0.03) but no increased risk in PFS or relapse. Conclusions: Using the CIBMTR registry, we report outcomes of relapsed DLBCL pts in a PR with residual PET/CT avid disease at time of autoHCT. While OS favored LCF pts, the adjusted 5-year PFS (41%) was comparable in both cohorts. This 5 year PFS is comparable to results reported in historical trials of auto-HCT for DLBCL. With no randomized data demonstrating superiority of CAR T-cell therapy in chemosensitive PR patients, these findings strongly support that autoHCT should remain the current standard of care for this patient population.