Comparison of central nervous system relapse outcomes following haploidentical vs identical-sibling transplant for acute lymphoblastic leukemia.

To explore the incidence, risk factors, and outcomes of central nervous system (CNS) relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) for acute lymphoblastic leukemia (ALL) and to compare the differences in CNS relapse between haploidentical donor HSCT (HID-HSCT) and HLA-identical sibling donor HSCT (ISD-HSCT). We performed a retrospective nested case-control study on patients with CNS relapse after allo-HSCT. The cumulative incidence of CNS relapse was 4.06% after allo-HSCT in ALL, with a significantly poor prognosis. The incidence was 3.91% and 5.36% in HID-HSCT and ISD-HSCT, respectively (p = .227). Among the patients with CNS relapse, the overall survival (OS) at 3 years was 56.2 ± 6.8% in the HID-HSCT subgroup and 76.9 ± 10.2% in the ISD-HSCT subgroup (p = .176). The 3-year cumulative incidence of systemic relapse was also comparable between the two subgroups (HID-HSCT, 40.6 ± 7.4%; ISD-HSCT, 13.3 ± 8.7%, respectively, p = .085). Younger age (p = .045), T-ALL (p = .035), hyperleukocytosis at diagnosis (p < .001), advanced disease stage at transplant (p < .001), pre-HSCT CNS involvement (p < .001), and absence of chronic graft vs host disease (cGVHD) (p < .001) were independent risk factors for CNS relapse after allo-HSCT. In conclusion, CNS relapse was a significant complication after allo-HSCT in ALL and was associated with poor prognosis. The incidences and outcomes were comparable between HID-HSCT and ISD-HSCT.