Reduced Intensity Vs. Myeloablative Conditioning Followed By Allogeneic Stem Cell Transplantation for Patients with Myelodysplastic Syndrome: Long Term Follow-up of a Prospective Randomized EBMT Phase III Study (RICMAC-Trial)

Introduction Retrospective studies in MDS/sAML suggest that reducing the intensity of the conditioning regimen prior to allogeneic stem cell transplantation reduces the risk of non-relapse mortality but is associated with a higher risk of relapse. A higher risk of relapse after RIC was confirmed in a prospective BMT CTN study but the prospective randomized studies from the EBMT for MDS and sAML did not show a difference in outcome after 2 years (J Clin Oncol. 2017 Jul 1;35(19):2157-2164). Here we present a long term follow-up of the study after a median follow-up of 75 months (range 4-150 months). Methods Within the European Society of Blood and Marrow Transplantation (EBMT) we conducted a prospective, multicenter, open label, randomized phase III trial comparing comparing a busulfan based (Busulfan 8mg/kg orally or equivalent dosis intravenously (iv) plus fludarabin 180mg/m²) reduced intensity conditioning regimen (RIC) and a standard myeloablative busulfan (Busulfan 16mg/kg orally or equivalent dosis iv plus cyclophosphamide 120mg/kg) based regimen (MAC) in patients with MDS or sAML ( Results In the first report (JCO 2017) the CI of NRM after 1 year was 17% (95% CI 8-26%) after RIC and 25% (95% CI 15-36%) after MAC (p = 0.29). The CI of relapse at 2 years was 17% (95% CI 8-26%) after RIC and 15% (95% CI 6-24%) after MAC (p = 0.6), resulting in a 2 year relapse-free and overall survival of 62% (95% CI 50-74%) and 76% (95% CI 66-87%) after RIC and 58% (95% CI 46-71%) and 63% (95% CI 51-75%) after MAC (p = 0.58 and p = 0.08, respectively). In the current follow-up study, all cases but one who were alive at last report could be updated. The median follow-up is now 75 months in the MAC and 72 months in the RIC arm. Since last follow-up =18 death occurred in both arm (MAC n=8, RIC n=10) 8 relapses (MAC n=4; RIC n=4) and 6 NRM (MAC n=2; RIC n=4). Second allogeneic stem cell transplantation was performed in 18 patients (n=10 in RIC and n=8 in MAC) due to graft failure (n=4) relapse (n=11) and others (n=3). The CI of chronic GvHD at 5 years was 65% (95% CI: 53-78) after RIC and 68% after MAC ((95% CI: 55-81; p = 0.70). At 5 years there was no difference in CI of NRM (22%, 95%CI: 12-32 vs 30% , 95%CI : 19-42, p=0.5) in CI of Relapse (22% , 95% CI: 12-32 vs18%, 95% CI: 8-28, p= 0.7), Relapse free- (57%, 95% CI: 44-69 vs51%, 95% CI: 39-64, p=0.8) and Overall survival (69%, 95% CI: 58-80 vs 53%, 95% CI: 40-65, p=0.15) between RIC and MAC, respectively. Conclusion This long term follow-up of the prospective randomized EBMT trial confirmed early results that RIC resulted in at least similar long term relapse-free and overall survival as MAC in patients with MDS or sAML. The trial was registered under ClinicalTrials.gov Identifier: NCT01203228. Disclosures Niederwieser: Miltenyi: Speakers Bureau; Novartis: Research Funding. Platzbecker:Celgene: Research Funding. Scheid:Celgene: Honoraria; Janssen: Honoraria; Novartis: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; BMS: Honoraria; Amgen: Honoraria. Stelljes:MSD: Consultancy; Amgen: Honoraria; JAZZ: Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Honoraria. Heim:Novartis: Research Funding. Bethge:Miltenyi Biotec GmbH: Consultancy, Honoraria, Research Funding; Neovii GmbH: Honoraria, Research Funding. Kobbe:Roche: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Celgene: Honoraria, Other: Travel Support, Research Funding.