Autologous peripheral blood stem cell transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia is safe but poses challenges for long-term maintenance of molecular remission: Results of the Auto-Ph17 study.

Autologous hematopoietic stem cell transplantation (SCT) is not a standard treatment option for Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL); however, its position has been reassessed since the introduction of tyrosine kinase inhibitors (TKIs). We prospectively analyzed the efficacy and safety of autologous peripheral blood SCT (auto-PBSCT) for Ph+ALL patients aged between 55 and 70 years who had achieved complete molecular remission. Melphalan, cyclophosphamide, etoposide, and dexamethasone were used for conditioning. A total of 12 courses of maintenance therapy, including dasatinib, were performed. The required number of CD34+ cells was harvested in all five patients. No patient died within 100 days after auto-PBSCT, and no unexpected serious adverse events were observed. Although 1-year event-free survival was 100%, hematological relapse was observed in three patients at a median of 801 days (range, 389-1088 days) after auto-PBSCT. Molecular progressive disease was observed in the other two patients, although they maintained their first hematological remission at the last visit. Auto-PBSCT can be safely performed for Ph+ALL with TKIs. A limitation of auto-PBSCT was suggested, despite the increase in the intensity of a single treatment. The development of long-term therapeutic strategies by including new molecular targeted drugs is warranted to maintain long-term molecular remission.