Results of unrelated transplantation for primary refractory/relapsed (ref/rel) acute myeloid leukemia (AML) were compared between 2 cohorts based on transplant year (2000-2009 and 2010-2019). The Cox proportional-hazards regression model was used for the multivariate analysis. There were a total of 3,430 patients included; 876 of them received a transplant between the years 2000 and 2009, and another 2,554 did between the years 2010 and 2019. The median follow-up time for the 2 groups was 8.7 (95% CI: 7.8-9.4) and 3.4 (95% CI: 3.1-3.6) years, respectively (P< 0.001). The median age was 52 years old (18-77) and 56 years old (18-79) (P > 0.0001), and 45.5% and 55.5%, respectively, had refractory AML, and 54.5% and 44.5% had relapsed AML. Myeloablative conditioning was used in 60% and 52% of cases. Both time periods had comparable rates of neutrophil recovery, day 100 incidence of acute graft-versus-host disease (GvHD), and 2-year incidence of chronic GvHD. The risk of relapse within 2 years after a transplant was greater among patients who had their procedure done between 2000 and 2009 (50.2%) compared to those who had their procedure done between 2010 and 2019 (45.1%) (HR, 0.85; 95% CI, 0.74-0.97; P = 0.002). The rates of leukemia-free survival (26% vs. 32.1%; HR, 0.87; 95% CI, 0.78-0.97; P = 0.01), overall survival (32.1 vs. 38.1%; HR, 0.86; 95% CI, 0.77-0.96; P = 0.01), and GvHD-free, relapse-free survival (21.5 vs. 25.3%; HR, 0.89; 95% CI, 0.81-0.99; Neither group had a substantially different rate of nonrelapse death after 2 years (23.8% versus 23.7%; HR, 0.91; 95% CI, 0.76-1.11; P = 0.34). Over the past 20 years, the success rate of unrelated donor transplantation has increased, allowing it to save the lives of around 1/3rd of patients with ref/rel AML.
