CML-111: Outcomes of Allogeneic Hematopoietic Cell Transplantation for Childhood Chronic Myeloid Leukemia: A Single Center Experience

Abstract

Context: Despite the apparent efficacy and favorable toxicity profile of TKIs, allogeneic HSCT remains the only curative treatment for CML, especially in younger patients, but transplant-related mortality should be considered. Objective: This study objective was to analyze the outcome of allogeneic HSCT in children with CML treated in a single center. Design/Setting: This is a retrospective study included children and adolescent patients (below 18 years of age) with confirmed CML who received an allogeneic HSCT at the stem cell transplantation unit of Children Cancer Hospital Egypt (CCHE 57357) between August 2007 and December 2017 with follow-up until June 2018. Patients or Other Participants: Out of 121 patients with newly diagnosed CML, 43 (35.5%) had available matched related donors and underwent HSCT, while 78 (64.5%) were maintained on TKI therapy. The median age at diagnosis was 12 years (range: 4.42 to 17.38 years), and the median time to transplant from diagnosis was 13 months. Intervention: All patients received Myeloablative conditioning chemotherapy containing BU/CY (busulfan in 16–20 mg/kg, and cyclophosphamide 4×50 mg/kg), with cyclosporine/short courses of MTX as GVHD prophylaxis. Patients with blastic crises received TKI therapy for one-year post HSCT. Main Outcomes Measures: Event-free survival, progression-free, and overall survival were measured. Incidence of GVHD and transplant-related mortality were also reported. Results: At initial diagnosis, there were 39 patients in chronic phase and 4 had blastic crises. Bone marrow harvest was the stem cell source in 32 patients, while 11 cases received mobilized peripheral blood stem cells with an average stem cell dose of 4.45×106/kg. The probabilities of overall survival and event-free survival at 5 years were 97.4% and 79.8%, respectively. TRM at 100 days and at 1-year post-transplant were 0%. The incidence of chronic GVHD was significantly higher in peripheral blood than bone marrow stem cell source (P=0.004). Conclusions: Considering the excellent survival rates and very low TRM, HSCT is still a valid option for pediatric patients with newly diagnosed CML, best using a bone marrow stem cell source to avoid a significant risk of cGVHD and its related complications.