Comparable outcomes of partially matched related and matched related allogeneic hematopoietic cell transplantation following reduced-intensity conditioning in adult patients with Philadelphia chromosome-negative acute lymphoblastic leukemia.

Reports from multiple centers have shown that reduced-intensity allogeneic hematopoietic cell transplantation (RIC-HCT) is able to benefit some adult patients suffering from Philadelphia chromosome-negative acute lymphoblastic leukemia (ALL). However, the relationship between donor cell source and outcome of RIC-HCT in (Ph-)ALL patients has not been elucidated. In this study, we present the outcome of 57 (Ph-)ALL patients treated with reduced-intensity conditioning (RIC) followed by HCT from HLA-matched related (MRD, n = 34) or HLA partially matched related (PMRD, n = 23) donors from a multicenter cohort. Neutrophil recovery at day 100 occurred in 91.3 % of the PMRD group and 97.1 % of the MRD group (P = 0.84). One hundred days after treatment, the cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) was 30.4 % (95 % confidence interval [CI], 13.0-53.0 %) in patients who received PMRD grafts, and 27.3 % (95 % CI, 15.0-48.0 %) for those who received MRD grafts (P = 0.76). The cumulative risk of developing chronic GVHD was 59.4 % (95 % CI, 31.0-72.0 %) in the MRD group and 23.4 % (95 % CI, 4.0-43.0 %) in the PMRD group (P = 0.03). The cumulative incidence of relapse in patients who received PMRD grafts was 18.8 % (95 % CI, 3.0-34.0 %), while for those who received MRD grafts it was 37.2 % (95 % CI, 15.0-48.0 %) (P = 0.32). Overall treatment-related mortality was 41.6 % (95 % CI, 20.0-62.0 %) in the PMRD group and 19.9 % (95 % CI, 7.0-35.0 %) in the MRD group (P = 0.08). Relapse was the most common cause of mortality in the MRD group, while infection contributed to the majority of deaths in the PMRD group. The 3-year probability of disease-free survival did not differ significantly between the two groups (55.5 % for the PMRD group vs. 48.4 % for the MRD group; P = 0.81). These data strongly suggest that RIC-HCT performed with PMRD may represent an alternative treatment option for adult patients with (Ph-)ALL.