Center effect on outcomes of second allogeneic hematopoietic stem cell transplantation for B-cell acute lymphoblastic leukemia: a nationwide retrospective study.

We evaluated the impact of center volume on outcomes in patients with B-cell acute lymphoblastic leukemia following their second allogeneic hematopoietic stem cell transplantation (allo-HSCT). Our cohort included 299 patients with relapse and 68 patients with graft failure after their first allo-HSCT between 2003 and 2017. Patients were stratified into low- and high-volume groups based on the number of allo-HSCT performed at each center. The primary endpoint was 5-year overall survival (OS) following the second allo-HSCT. In the relapse cohort, the high-volume group demonstrated significantly better 5-year OS (21.1% vs 13.6%, P = 0.0062) and progression-free survival (16.1% vs 10.6%, P = 0.010). Multivariate analysis showed that high-volume group was a favorable factor for OS (hazard ratio [HR]: 0.72, 95% confidence interval [CI]: 0.56-0.94, P = 0.016). This survival benefit was consistent in both Philadelphia chromosome-negative (HR: 0.71, 95% CI: 0.51-0.99, P = 0.042) and positive (HR: 0.61, 95% CI: 0.39-0.95, P = 0.030) subcohorts. In the graft failure cohort, the high-volume group showed a trend toward better 5-year OS (41.6% vs 24.4%, P = 0.098) and lower 5-year nonrelapse mortality (NRM) (55.9% vs 75.6%, P = 0.067). Multivariate analysis confirmed the protective effect of the high-volume group on NRM (HR: 0.55, 95% CI: 0.30-0.99, P = 0.044). Our findings demonstrate that center volume significantly impacts outcomes after the second allo-HSCT regardless of indication, highlighting the need for inter-center collaboration and standardized management strategies for this high-risk population.