RT Journal Article T1 Post-Transplantation Cyclophosphamide for Graft-versus- Host Disease Prophylaxis in Multiple Myeloma Patients Who Underwent Allogeneic Hematopoietic Cell Transplantation: First Comparison by Donor Type. A Study from the Chronic Malignancies Working Party of the European Society for Blood and Marrow Transplantation. A1 Sahebi, Firoozeh A1 Eikema, Dirk-Jan A1 Koster, Linda A1 Kroger, Nicolaus A1 Meijer, Ellen A1 van Doesum, Jaap A A1 Rovira, Montserrat A1 Koc, Yener A1 Angelucci, Emanuele A1 Blaise, Didier A1 Sammassimo, Simona A1 McDonald, Andrew A1 Arroyo, Concepcion Herrera A1 Sanchez, James F A1 Forcade, Edouard A1 Castagna, Luca A1 Stölzel, Friedrich A1 Sanz, Jaime A1 Tischer, Johanna A1 Ciceri, Fabio A1 Valcarcel, David A1 Proia, Anna A1 Hayden, Patrick J A1 Beksac, Meral A1 Yakoub-Agha, Ibrahim A1 Schönland, Stefan K1 clinical research K1 engraftment K1 hematology K1 multiple myeloma K1 transplantation AB Graft-versus-host disease (GVHD) remains among the major causes of treatment failure in patients with multiple myeloma (MM) undergoing allogeneic hematopoietic cell transplantation (allo-HCT). The use of post-transplantation cyclophosphamide (PT-Cy) is now a well-established and widely used method for GVHD prophylaxis after HLA haploidentical HCT. However, the rationale for using PT-Cy in the setting of matched donor transplantation is less apparent, given the lesser degree of bidirectional alloreactivity. In this retrospective study, we investigated the role of PT-Cy as GVHD prophylaxis in patients with multiple myeloma underoing allo-HCT, among different donor types, to determine cumulative incidence of acute and chronic GVHD and impact on engraftment, progression-free survival (PFS), GVHD-free/relapse- free survival (GRFS), overall survival (OS), and NRM A total of 295 patients with MM underwent allo-HCT using grafts from a matched related donor (MRD; n = 67), matched unrelated donor (MUD; n = 72), mismatched related or unrelated donor (MMRD/MMUD, 1 antigen; n = 27), or haploidentical donor (haplo; n = 129) using PT-Cy between 2012 and 2018. In addition to PT-Cy, agents used in GVHD prophylaxis included calcineurin inhibitors in 239 patients (81%), with mycophenolate mofetil in 184 of those 239 (77%). For grade II-IV acute GVHD, the cumulative incidence at day +100 was 30% (95% confidence interval [CI], 25% to 36%), 9% (95% CI, 5% to 12%) for grade III-IV acute GVHD, and 27% (95% CI, 21% to 32%) for chronic GVHD (limited, 21%; extensive, 6%), with no differences by donor type. The median time to neutrophil engraftment was 19d (95% CI, 18-19), with no significant difference by donor type. The median time to platelet engraftment was delayed in haploidentical donor graft recipients (27 days versus 21 days; P YR 2021 FD 2021-09-17 LK https://hdl.handle.net/10668/25369 UL https://hdl.handle.net/10668/25369 LA en DS RISalud RD Apr 5, 2025