This study investigated the efficacy of imatinib based therapy with intensified consolidation therapy in patients with Philadelphia chromosome (Ph)-positive acute lymphoblastic leukemia (ALL) to prevent early relapse. We conducted a phase II trial of imatinib-combined chemotherapy for newly diagnosed BCR-ABL-positive ALL in adults. Sixty-eight patients were included in the trial between October 2008 and December 2010. The median age was 49 years, with 28 patients >55 years of age. Sixty-five patients achieved CR (95.6%). The estimated 2-year event-free survival (EFS) and overall survival (OS) were 62.3% and 67.4%, respectively. Allogeneic stem cell transplantation (allo-SCT) at initial CR was performed in 43 patients. Thirty-five of 39 patients <55 years and 8 of 26 patients >55 years underwent allo-SCT at first CR. The 3-year OS in patients <55 years receiving allo-SCT at first CR, patients >55 years receiving allo-SCT at first CR, patients <55 years not receiving allo-SCT at first CR, and patients >55 years not receiving allo-SCT at first CR were 80.4%, 41.1%, 32.5%, and 52.0%, respectively (P = 0.058). The three-year EFS in each group was 76.7%, 53.6%, not reached, and 26.4%, respectively (P = 0.150). A high CR rate was observed with imatinib-based chemotherapy allowing allo-SCT in a high proportion of patients, particularly those <55 years. Moreover, intensified consolidation therapy reduced early relapse rates following induction therapy and resulted in improved OS and EFS rates following allo-SCT. This trial was registered with the UMIN (000001226).
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