Comparison of microtransplantation,chemotherapy and allogeneic transplantation in post-remission therapy for Philadelphia chromosome-positive acute lymphoblastic leukemia

Patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph⁺ ALL) have poor prognosis, and the efficacy of chemotherapy plus tyrosine kinase inhibitors (TKIs) followed by mismatched donor stem cell infusion (microtransplantation, MST) has not been determined. We retrospectively summarized 45 patients including 11 undergoing MST with TKIs, 17 receiving allogeneic transplant and 17 undergoing chemotherapy with TKIs. Improved 4-year overall survival rate was observed in the MST group (91%) compared with either transplant group (31%, P = .005) or chemotherapy group (36%, P = .013). The MST group also had higher 2-year and 4-year leukemia-free survival rates (91% and 72%, respectively) compared with either transplant group (33%, P = .005 and 33%, P = .021, respectively) or chemotherapy group (41%, P = .017 and 31%, P = .023, respectively). 2-year and 4-year cumulative incidences of hematologic relapse were lower in the MST group (9% and 28%, respectively) compared with those in the chemotherapy group (56%, P = .025 and 67%, P = .034, respectively). In patients undergoing MST, donor microchimerism was detected (1.07 × 10^-5 to 6.6 × 10^-4 copies from 9 to 1499 days) in 7 patients, and donor/patient-derived HLA*0201/2402⁺WT1⁺CD8⁺ T cells were found from 0.05% to 0.67% in 6 patients. MST may provide a favorable treatment for patients with Ph⁺ ALL.