Comparison of Conditioning Regimens for Allogeneic Hematopoietic Cell Transplantation in Non-Hodgkin Lymphoma

Abstract

<h3>Background</h3> Allogeneic hematopoietic cell transplantation (allo-HCT) allows for the possibility of cure in patients (pts) with Non-Hodgkin Lymphoma (NHL) as it provides an immunologic graft-versus-lymphoma effect. Non-relapse mortality (NRM) was prohibitive in myeloablative regimens, but technical advances with the advent of reduced-intensity conditioning (RIC) or nonmyeloablative (NMA) regimens have decreased these rates. RIC regimens are generally associated with more toxicity and higher NRM than NMA regimens. Though studies showed both approaches are safe and effective, there is lack of direct comparison between these different intensities in NHL. <h3>Methods</h3> This retrospective study identified pts aged ≥ 18 years who underwent allo-HCT for relapsed/refractory NHL between 3/2008-6/2017 at our center. Outcomes were compared between pts who received NMA and RIC conditioning, with intensity defined per CIBMTR. Progression-free survival (PFS) was the primary outcome. Secondary outcomes included overall survival (OS) and non-relapse mortality (NRM). Additional outcomes included rates of acute GVHD at Day 100, chronic GVHD, and CMV reactivation at Day 100. Regimen intensity and other variables significant by univariate analysis were included in the multivariate analysis <h3>Results</h3> For the 144 pts identified, median age was 56 years (range, 19-79). More pts received NMA regimens (n=80, 56%) and most did not undergo prior autologous HCT (n=103, 72%). NMA regimens were given more frequently to pts with indolent B-cell lymphoma and were more likely to receive ATG and/or rituximab (p = 0.008, p < 0.001, and p < 0.001, respectively). At a median overall follow-up of 57.8 months (range 49 - 75.1) neither median PFS or OS were reached. In univariate analysis, NMA conditioning was associated with a longer PFS than RIC [HR 1.9 (1.11-3.24), p = 0.019). No difference was found in OS [HR 1.56 (0.85-2.85), p = 0.15). There was an increase in all grades of aGVHD [HR 3.68 (2.16, 6.28), p < 0.001)] with RIC regimens, but only 12 events of grade III/IV aGVHD overall. In multivariate analyses (with histology and ATG as covariates) NMA with rituximab had improved PFS compared to RIC without rituximab [HR 0.43 (95% CI 0.22, 0.81; p=0.009)]. However, PFS was similar comparing NMA and RIC groups [HR 0.72 (95% CI 0.37, 1.41; p=0.3)]. Similarly, aGVHD (any grade) risk was lower in NMA pts receiving rituximab compared to RIC pts who did not [HR 0.15 (0.07-0.32), p < 0.001). No significant differences were noted in NRM or CMV reactivation between groups. <h3>Conclusion</h3> Our study suggests that there are comparable and favorable outcomes between RIC and NMA regimens in allo-HCT for NHL with careful patient and regimen selection. Further studies are needed to better define criteria in choosing between NMA and RIC allo-HCT regimens for pts with NHL.