The Role of Allogeneic Transplant for Adult Ph+ ALL in CR1 with Complete Molecular Remission: A Retrospective Analysis.

Historically, Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) has been associated with poor outcomes and allogeneic hematopoietic cell transplantation (allo-HCT) is recommended in first complete remission (CR1). However, in the tyrosine kinase inhibitor (TKI) era, rapid attainment of a complete molecular remission (CMR) is associated with excellent outcomes without allo-HCT, suggesting transplant may not be required for these patients. To test this hypothesis, we retrospectively identified adult patients with Ph+ ALL treated with induction therapy including TKIs and attained CMR within 90 days of diagnosis at 5 transplant centers in the United States. We compared outcomes of those who did and did not receive allo-HCT in first remission. We identified 230 patients (Allo-HCT: 98, non-HCT: 132). The allo-HCT cohort was younger with better performance status. On multivariable analysis (MVA), allo-HCT was not associated with improved overall survival (aHR 1.05, 95% C.I. 0.63 - 1.73) or relapse-free survival (aHR: 0.86, 95% C.I. 0.54 - 1.37) compared to non-HCT treatment. Allo-HCT was associated with a lower cumulative incidence of relapse (aHR 0.32, 95% C.I. 0.17 - 0.62) but higher non-relapse mortality (aHR: 2.59, 95% C.I. 1.37 - 4.89). Propensity score matching analysis confirmed results of MVA. Comparison of reduced-intensity HCT to non-HCT showed no statistically significant difference in any of the above endpoints. In conclusion, adult patients with Ph+ ALL who achieved CMR within 90 days of starting treatment did not derive a survival benefit from allo-HCT in CR1 in this retrospective study.