Prognostic factors and outcomes of unrelated bone marrow transplantation for Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ALL) pre-treated with tyrosine kinase inhibitors.

Background: The treatment and prognosis of Acute Lymphoblastic Leukemia (ALL), including Philadelphia chromosome positive ALL (Ph+ALL), a poor prognostic factor, has changed with the introduction of tyrosine kinase inhibitors (TKIs). Nevertheless, allogeneic hematopoietic cell transplantation (allo-HCT) is still recommended as the first-line curative treatment. To date, no study has investigated the prognostic factors and outcomes of unrelated bone marrow transplantation (u-BMT) for Ph+ALL following pre-transplant treatment with a TKI-containing regimen.

Methods: We retrospectively evaluated 15 transplantations of 14 patients with Ph+ALL pre-treated with a TKI-containing regimen at our institute. The 14 patients comprised 11 males and 3 females, with a median age of 50 years (range: 19-64). We performed univariate and multivariate analyses of risk factors that contributed to overall survival (OS) or leukemia-free survival (LFS).

Results: Three-year OS of the patients with molecular complete remission (MCR) and with non-MCR at transplantation were 89% and 40% (p = 0.006), respectively, and three-year LFS rates were 79% and 0% (p = 0.001), respectively. Univariate analysis revealed that first hematological complete remission (HCR1) and MCR at transplant were significantly related to better OS and LFS. Multivariate analysis showed that MCR at transplant was significantly associated with better OS and LFS.

Conclusions: In agreement with a previous study that included other stem cell sources, u-BMT was deemed feasible for the treatment of Ph+ALL. Analysis of a larger cohort is required to clarify the prognostic factors that affect transplant outcome in Ph+ALL since the introduction of TKIs.