Favorable outcome of allogeneic hematopoietic stem cell transplantation followed by post-transplant treatment with imatinib in children with Philadelphia chromosome-positive acute lymphoblastic leukemia

BACKGROUND Allogeneic hematopoietic stem cell transplantation (HSCT) is the preferred curative therapy for children with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). We evaluated the treatment outcomes of children with Ph+ ALL who underwent allogeneic HSCT. METHODS Fifteen children diagnosed with Ph+ ALL in Asan Medical Center Children's Hospital between 1998 and 2012 were retrospectively analyzed. RESULTS Of 521 children diagnosed with ALL during the study period, 15 had a Philadelphia chromosome. Among these 15 patients, 13 attained complete remission (CR) following induction chemotherapy, and two died of intracerebral hemorrhage during leukapheresis and induction chemotherapy, respectively. Of the 13 patients who attained CR, 12 received allogeneic HSCT, mainly from unrelated donors. Of the 12 patients who received HSCT, one died of a transplant-related cause, one died of relapse after HSCT, and 10 remain in continuous CR. Of the 10 patients who remained in CR longer than six months after HSCT, seven received post-HSCT imatinib. For all 15 patients, the 5-year overall survival, event-free survival, and cumulative incidence of relapse were 60.0%, 48.6%, and 38.8%, respectively, with a median follow-up of 70 months. For the HSCT group, the 5-year overall survival, event-free survival, and cumulative incidence of relapse were 80.2%, 72.9%, and 29.3%, respectively, with a median follow-up of 100 months. CONCLUSION Allogeneic HSCT cures a significant proportion of Ph+ ALL patients. Because the use of imatinib appears to be a promising approach, strategies that include tyrosine kinase inhibitors before and after HSCT require further evaluation.