CML-451: Outcomes of Allogeneic Stem Cell Transplant in Chronic Myeloid Leukemia Blast Phase: A Single Center Experience from South India

Context: Blast phase (BP) remains a significant challenge in the treatment of chronic myeloid leukemia (CML). Currently, allogeneic stem cell transplant (AlloSCT) remains the best chance of cure for BP, with 3-year survival ranging from 35–40%. Outcomes of AlloSCT are better when performed in the second chronic phase. Objective: There is limited contemporary data of AlloSCT in CML-BP from resource-limited settings. We hereby present our experience of AlloSCT in patients with CML-BP Design: Retrospective study of CML-BP patients who underwent AlloSCT between October 2017 to July 2019. Median follow-up was 24 months. Setting: Tertiary institution with developing transplant unit. Patients or Other Participants: Seven CML-BP (WHO criteria) patients underwent AlloSCT at our center after reverting to chronic phase. Interventions: All patients received myeloablative conditioning and stem cells harvested from peripheral blood. Main Outcomes Measures: Leukemia-free survival (LFS) was defined as the time from the AlloSCT to relapse or death due to any cause. Overall survival (OS) was the time from AlloSCT to death due to any cause. Results: The median age was 40 years (range, 9–52), and the male-to-female ratio was 5:2. Four patients had de novo BP; the subtype of BP was lymphoid in three, myeloid in three, and mixed phenotypic (B/myeloid) in one. The median time from the diagnosis to ASCT was 6 (3–12) months. The median CD34+ dose was 7.6 (range, 6.6–8.9) x106 cells/kg. Peri-transplant toxicities within the first 100 days included febrile neutropenia with septic shock in three, cytomegalovirus (CMV) reactivation in three, ≥ grade 3 mucositis in two patients, secondary graft failure (SGF) in one, and poor graft function (PGF) in one. In both patients who had a haploidentical donor transplant, one had SGF and one had PGF. Day 100 transplant-related mortality (TRM) was observed in two patients, disseminated infections being the cause of death for both. Post-AlloSCT, all living patients received dasatinib maintenance starting at a median of 50 (47–60) days. On the last follow-up on April 30, 2021, two-year PFS and OS were 43% and 57%, respectively. Conclusions: AlloSCT can result in promising survival for carefully selected patients of CML-BP, especially with a matched sibling donor. The adverse outcome for both the haplo-transplant patients underscores the need for careful donor selection and reflects the initial learning curve. None of the authors have any relevant conflicts of interest to declare.