High Complete Remission Rate and Promising Outcome by Combination of Imatinib and Chemotherapy for Newly Diagnosed BCR-ABL–Positive Acute Lymphoblastic Leukemia: A Phase II Study by the Japan Adult Leukemia Study Group

Abstract

Purpose: A novel therapeutic approach is urgently needed for BCR-ABL–positive acute lymphoblastic leukemia (ALL). In this study, we assessed the efficacy and feasibility of chemotherapy combined with imatinib. Patients and Methods: A phase II study of imatinib-combined chemotherapy was conducted for newly diagnosed BCR-ABL–positive ALL in adults. Eighty patients were entered into the trial between September 2002 and January 2005. Results: Remission induction therapy resulted in complete remission (CR) in 77 patients (96.2%), resistant disease in one patient, and early death in two patients, as well as polymerase chain reaction negativity of bone marrow in 71.3%. The profile and incidence of severe toxicity were not different from those associated with our historic chemotherapy-alone regimen. Relapse occurred in 20 patients after median CR duration of 5.2 months. Allogeneic hematopoietic stem-cell transplantation (HSCT) was performed for 49 patients, 39 of whom underwent transplantation during their first CR. The 1-year event-free and overall survival (OS) rates were estimated to be 60.0%, and 76.1%, respectively, which were significantly better than those for our historic controls treated with chemotherapy alone (P < .0001 for both). Among the current trial patients, the probability for OS at 1 year was 73.3% for those who underwent allogeneic HSCT, and 84.8% for those who did not. Conclusion: Our results demonstrated that imatinib-combined regimen is effective and feasible for newly diagnosed BCR-ABL–positive ALL. Despite a relatively short period of observation, a major potential of this treatment is recognized. Longer follow-up is required to determine its overall effect on survival.