Philadelphia chromosome-positive mixed phenotype acute leukemia in the imatinib era

Although the introduction of imatinib dramatically improved the outcomes for patients with Philadelphia chromosome-positive B-cell precursor acute lymphoblastic leukemia (Ph + BCP-ALL), the survival benefit of imatinib has not been assessed in the context of Ph + mixed phenotype acute leukemia (Ph + MPAL). To clarify this important issue, we studied 42 Ph+ acute leukemia (Ph + AL) patients who received intensive chemotherapy and concurrent administration of imatinib. Of the 42 Ph + AL patients, 13 (31%) patients were categorized as Ph + MPAL (positive for both myeloid and B-cell lineage), 27 (64%) were categorized as Ph + BCP-ALL, and two (5%) were categorized as Ph + acute myeloid leukemia. The complete remission rates after the initial induction therapy were not significantly different when comparing Ph + MPAL and Ph + BCP-ALL patients (100% vs. 85%, respectively, P = 0.14). Likewise, there were no significant differences in the 5-yr overall survival (OS) or disease-free survival (DFS) rates when comparing the MPAL and BCP-ALL groups (OS: 55% vs. 53%, respectively, P = 0.87, DFS: 46% vs. 42%, respectively, P = 0.94). These findings suggest that concurrent imatinib administration with chemotherapy improved the outcomes of Ph + MPAL patients to the level seen in Ph+BCP-ALL patients and should, therefore, be considered as the standard therapy for these patients.