Haploidentical Vs. Matched Unrelated Donor Transplants Using Post-Transplant Cyclophosphamide for Lymphoma: A Joint CIBMTR/EBMT Study
Authors: Mussetti Alberto , Kanate Abraham S. , Wang Tao , He Meilun , Hamadani Mehdi , Finel Hervé , Boumendil Ariane , Glass Bertram , Castagna Luca , Blaise Didier , Marsh Steven G.E. , Paczesny Sophie , Gadalla Shahinaz M. , Dreger Peter , Spellman Stephen R. , Lee Stephanie J. , Bolon Yung-Tsi , Sureda Anna 
Published: November 2021

Abstract
Introduction: Post-transplant cyclophosphamide (PTCy) is a standard GVHD prophylactic approach for haploidentical hematopoietic cell transplantation (haploHCT). Retrospective studies in patients with lymphoma showed lower chronic GVHD in haploHCT with PTCy-based GVHD prophylaxis compared to matched unrelated donor (MUD) HCT with calcineurin-based GVHD prophylaxis (+/- ATG). Recent retrospective studies showed that using MUD donors was better than haplo donors when PTCy and reduced-intensity conditioning are used for ALL, AML or MDS. However, no studies to date have compared haploHCT and MUD HCT when PTCy is used in the setting of lymphomas.

Methods: 2155 adults (730 CIBMTR, 1425 EBMT) aged =/&gt;18 years who received their first haploHCT or MUD HCT (8/8 match at HLA-loci A, B, C and DRB1) using PTCy from 2010-2019 for lymphoma were included. The majority of both MUD (n=312; 14%) and haplo (n=1843; 86%) HCTs received reduced intensity/non-myeloablative conditioning (n=1655; 77%) using a peripheral blood stem cell graft (n=1379; 64%) and a three-drug GVHD prophylaxis (PTCy + calcineurin inhibitor + MMF, n=1805; 84%). Hodgkin's lymphoma was the most common indication (n=899; 42%) followed by diffuse large B-cell lymphoma (n=525; 24%), T-cell lymphomas (n=328; 15%), mantle cell lymphoma (n=234; 11%) and follicular lymphoma (n=169; 8%). Most had chemosensitive disease at transplant (n=1781; 83%). Some main characteristics of the two cohorts are shown in Figure 1. Median follow-up among survivors was longer for haplo-HCT (36 and 31 months for the CIBMTR and EBMT cohort, respectively) than MUD-HCT (24 and 17 months, respectively). Cox proportional hazards models were built using stepwise forward and backward selection with a selection/retention threshold of 0.05. Any clinical variables that did not meet the proportional hazard assumption were adjusted for by stratification, and regression models were built to compare outcomes between donor types. Center effect was adjusted in all the models.
Results: Figures 2 and 3 show the multivariate analysis results. Overall survival was 73% (71-75%) at 1 year and 65% (63-67%) at 2 years. Relapse was 21% (20-23%) at 1 year and 26% (24-28%) at 2 years. All outcomes favored MUD over haplo donors with the use of PTCy-based GVHD prophylaxis for both.
Conclusions: Patients with lymphoma receiving PTCy HCT from MUDs demonstrated better outcomes than those with haplo donors in this retrospective study of CIBMTR and EBMT data Future prospective studies are needed to confirm and clarify the reasons for these differences.
Figure 1 Figure 1.

Disclosures
Mussetti: GILEAD: Other: Clinical trials participation, Research Funding; TAKEDA: Honoraria; NOVARTIS: Honoraria, Other: Clinical trials participation. Hamadani: Janssen, Incyte, ADC Therapeutics, Omeros, Morphosys, Kite: Consultancy; Sanofi, Genzyme, AstraZeneca, BeiGene: Speakers Bureau; Takeda, Spectrum Pharmaceuticals and Astellas Pharma: Research Funding. Glass: Novartis: Consultancy; Riemser: Research Funding; Helios Klinik Berlin-Buch: Current Employment; Kite: Consultancy; Roche: Consultancy, Research Funding, Speakers Bureau; BMS: Consultancy. Blaise: Jazz Pharmaceuticals: Honoraria. Paczesny: Medical University of South Carolina: Patents & Royalties: inventor on the ST2 bispecific antibody patent application. Dreger: Novartis: Consultancy, Speakers Bureau; Riemser: Consultancy, Research Funding, Speakers Bureau; BMS: Consultancy; Bluebird Bio: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; Gilead Sciences: Consultancy, Speakers Bureau; Janssen: Consultancy; AbbVie: Consultancy, Speakers Bureau; Roche: Consultancy, Speakers Bureau. Lee: AstraZeneca: Research Funding; Incyte: Research Funding; Janssen: Other; Kadmon: Research Funding; National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Syndax: Research Funding; Pfizer: Research Funding; Takeda: Research Funding; Amgen: Research Funding. Sureda: BMS/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Speakers Bureau; Bluebird: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite, a Gilead Company: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Mundipharma: Consultancy; Roche: Other: Support for attending meetings and/or travel; GSK: Consultancy, Honoraria, Speakers Bureau.