Allogeneic Stem Cell Transplantation for Pediatric and Adolescent Patients with CML: Results from the Prospective Trial CML-paed I

Purpose: Stem cell transplantation (SCT) can definitely cure chronic myeloid leukemia (CML), a rare disease in childhood. We prospectively evaluated the results of early SCT in pediatric CML after standardized pretreatment with hydroxyurea interferon. Patients and Methods: Between 1995 and 2004, 200 children (median age: 12.4 years) were enrolled and stratified: given the availability of an HLA-matched related donor (MRD), SCT was scheduled within 6 months and otherwise from an unrelated donor (UD) within 12 months following diagnosis. Results: 176 patients underwent SCT; from MRD within median 4 months and from UD within median 11 months after diagnosis. At SCT, 158 patients were in chronic phase (CP1 or CP2), 9 patients were in accelerated phase and 9 patients were in blast crisis (BC) The conditioning regimen - total body irradiation or busulfan - exerted no different impact on overall survival (OS). Probability of OS at 5 years was 87+/-11% if grafted from a sibling (n =41), 52+/-9% from matched UD (MUD, n=71), and 45+/-16% from mismatched donors (MMD, n=55), respectively. A trend for better OS in CP1 was observed if SCT was performed within 6 months (n = 49; 74+/-9%), compared to 7-12 months (n=52; 62+/-15%), and >12 months (n=43; 62+/-17%) after diagnosis, respectively (p = 0.157). Probability of relapse at 5 years was 20+/-12%. Transplant-related mortality and graft-versus-host disease mainly contributed to the inferior outcome in UD and HLA-mismatched SCT. Conclusion: These data from the first prospective trial on CML restricted to children and adolescents might be considered for decision making when balancing the risks of SCT against the increasing use of imatinib as upfront treatment for CML.