Dasatinib-based Two-step Induction for Adults with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia.

The standard treatment for adults with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) in Japan is imatinib-based chemotherapy followed by allogeneic hematopoietic stem cell transplantation (HSCT). However, approximately 40% of patients cannot undergo HSCT in their first complete remission (CR1) because of chemotherapy-related toxicities and relapse before HSCT, and older age. We evaluated dasatinib-based two-step induction with the primary endpoint of 3-year event-free survival (EFS) in this study. The first induction (IND1) was dasatinib plus prednisolone to achieve CR and the second (IND2) was dasatinib plus intensive chemotherapy to achieve minimal residual disease (MRD)-negativity. Patients who achieved CR and had an appropriate donor were recommended to undergo HSCT during a consolidation phase later than the first consolidation, which included high-dose methotrexate. Prophylactic dasatinib after HSCT was assigned to patients with positive pre-transplant MRD. All 78 eligible patients achieved CR or incomplete CR after IND1, and 52.6% achieved MRD-negativity after IND2. Non-relapse mortality (NRM) was not reported. T315I mutation was detected in all 4 hematological relapses before HSCT. Fifty-eight (74.4%) patients underwent HSCT in CR1 and 44 (75.9%) were negative with pre-transplant MRD. At a median follow-up of 4.0 years, the 3-year EFS and overall survival were 66.2% (95% confidence interval [CI], 54.4-75.5) and 80.5% (95% CI, 69.7-87.7), respectively. The cumulative incidence of relapse and NRM at 3 years from enrollment were 26.1% and 7.8%, respectively. Dasatinib-based two-step induction was demonstrated to improve the 3-year EFS. This study was registered in the UMIN Clinical Trial Registry as #UMIN000012173.