Peripheral blood haploidentical allogeneic stem cell transplantation in older adults with acute myeloid leukemia and myelodysplastic syndromes demonstrates long term survival, results from the Australasian Bone Marrow Transplant Recipient Registry

Abstract

BACKGROUND: There is a limited body of evidence for Haploidentical Hematopoietic Stem Cell Transplantation (Haplo-HSCT) in older patients. Previous studies have used a high proportion of bone marrow derived grafts and a variety of conditioning regimens. In Australia and New Zealand, Haplo-HCST is predominantly performed using peripheral blood (PB) with universal use of post-transplant cyclophosphamide (PTCy). OBJECTIVE: To characterize the outcomes of older recipients undergoing Haplo-HSCT for Acute Myeloid Leukaemia (AML) and Myelodysplastic Syndromes (MDS). STUDY DESIGN: Data was collected through the Australasian Bone Marrow Transplant Recipient Registry (ABMTRR) for patients aged 65 or older receiving a PB Haplo-HSCT for AML/MDS between January 2010 and July 2020 RESULTS: A total of 44 patients were included in the analysis. The median follow-up time was 377 days. The median age was 68 (range 65-74) with a median Karnofsky Performance Status of 90. Thirty patients (68.2%) had AML while 14 (31.8%) had MDS. The median donor age was 40. The most common conditioning regimen was non-myeloablative fludarabine, cyclophosphamide and TBI (75%), the remainder of the patients received either melphalan or busulfan based regimens, the majority were reduced intensity with only 2 patients undergoing myeloablative conditioning. All patients received post-transplant cyclophosphamide and mycophenolate mofetil with the majority also receiving tacrolimus (90.5%) and the remainder receiving cyclosporin (9.5%). No patients received anti-thymocyte globulin. Neutrophil engraftment was achieved in 97.6% of patients, at a median of 18 days while platelet engraftment was achieved in 92.7% of patients at a median of 28 days. The cumulative incidences of CMV reactivation and CMV disease were 52.5% and 5.1% at 1 year. The incidence of grade 2-4 acute Graft Versus Host Disease (GVHD) was 18.2%. The incidence of chronic GVHD at 2 years was 40.7%, with extensive chronic GVHD occurring in 17.7% of patients. The incidences of relapse and non-relapse mortality (NRM) at 2 years were 8.8% and 20.7% respectively. The leading causes of death were infection (64.7%) followed by relapse (14.2%). The 2-year overall survival was 74%. Relapse free survival and GVHD free, relapse free survival at 2 years was 70% and 48%. CONCLUSION: Haplo-HSCT using a peripheral blood graft and PTCy GVHD prophylaxis demonstrates long-term disease control with acceptable rates of NRM for older patients with AML/MDS.