Reduced Intensity Compared to Non-myeloablative Conditioning in Patients with Non-Hodgkin Lymphoma undergoing Allogeneic Hematopoietic Stem Cell Transplantation

. Reduced intensity (RIC) and non-myeloablative (NMA) conditioning are preferred for patients with non-Hodgkin lymphoma (NHL) receiving allogeneic hematopoietic stem cell transplantation (allo-HCT). Although prior studies have suggested that higher-intensity regimens within RIC-NMA conditioning are associated with inferior outcomes in patients with NHL, the optimal conditioning regimen remains unknown.. We performed a retrospective single-center analysis to determine outcomes of adult patients with B- and T-cell NHL who underwent allo-HCT and received either RIC or NMA conditioning between March 2008 - December 2019. RIC regimens included fludarabine-cyclophosphamide-thiotepa-4Gy-total body irradiation (Flu-Cy-TT-4Gy-TBI), fludarabine-melphalan (Flu-Mel), fludarabine-cyclophosphamide-4Gy-total body irradiation (Flu-Cy-4Gy-TBI) and fludarabine-busulfan-4 (Flu-Bu-4). The NMA regimen included fludarabine-cyclophosphamide-2Gy-total body irradiation (Flu-Cy-2Gy-TBI). The primary outcome was overall survival. Secondary outcomes included progression-free survival, non-relapse mortality and the incidence of acute and chronic graft-vs-host-disease (GvHD).. Of 279 transplanted patients (median age, 58 years), 110 received RIC (55% Flu-Mel, 38% Flu-Cy-TT-4Gy-TBI, 6% Flu-Bu-4, 1% Flu-Cy-4Gy-TBI) and 169 received NMA conditioning with Flu-Cy-2Gy-TBI. With a median of 64 months of follow-up from allo-HCT, there was no significant difference in overall survival between the NMA and RIC groups (median not reached [NR] vs 103 months, respectively. P = 0.1), and this was maintained on multivariable analysis. Similarly, after adjustment for all independently significant covariates (age, Karnofsky performance status, HCT-CI, disease histology), the regression analysis showed no significant difference in progression-free survival with RIC compared to NMA conditioning (hazard ratio [HR] 1.38; 95% CI 0.92 - 2.09, P = 0.24). On univariable analysis, there was no significant difference in non-relapse mortality between RIC and NMA conditioning (100-day estimates: 10.0% vs. 1.8%, respectively, P = 0.5). After adjustment for age, ethnicity, Karnofsky performance score, HCT-CI, GvHD prophylaxis and donor source, RIC conditioning was associated with a significantly higher incidence of non-relapse mortality compared to NMA conditioning (HR 2.61, 95% CI 1.04 - 6.52, P = 0.039). On multivariable analysis, compared with the Flu-Cy-2Gy-TBI regimen, the RIC cohort had higher rates of grade II-IV (HR, 2.25; 95% CI, 1.31 - 3.86; P = 0.002) and grade III-IV acute GvHD (HR, 5.62; 95% CI, 2.03 - 15.6; P < 0.001).. The findings of this study suggest that NMA conditioning with Flu-Cy-TBI-2Gy may be considered over more intensive RIC regimens for patients with NHL undergoing allo-HCT.