Allogeneic Hematopoietic Cell Transplantation for Patients with Relapsed Acute Promyelocytic Leukemia.

Although autologous hematopoietic cell transplantation (HCT) is an established therapy for patients with relapsed acute promyelocytic leukemia (APL) after returning to complete remission (CR), the role of allogeneic HCT remains unclear for treating relapsed APL. This study aimed to investigate allogeneic HCT outcomes in patients with relapsed APL, focusing particularly on those who underwent transplantation in non-CR and those who had relapsed after prior autologous HCT. We retrospectively analyzed Japanese nationwide transplantation registry data of patients with relapsed APL age ≥16 years who underwent allogeneic HCT between 2006 and 2020. A total of 195 patients were eligible for this analysis, including 69 who underwent transplantation in non-CR and 55 who relapsed after prior autologous HCT. The median duration of follow-up for survivors was 5.4 years. Multivariate analysis revealed that both non-CR at transplantation (hazard ratio [HR], 1.74; 95% confidence interval [CI], 1.12 to 2.71; P = .014) and prior autologous HCT (HR, 2.10; 95% CI, 1.28 to 3.44; P = .013) were associated with higher risks of overall mortality. The 5-year overall survival (OS) rates for patients who underwent transplantation in CR and non-CR were 58% and 39%, respectively (P = .085), if they did not have a history of prior autologous HCT. In the patients who had relapsed after prior autologous HCT, the 5-year OS rate was 47% for those who underwent allogeneic HCT in CR and 6% for those who did so in non-CR (P = .001). Allogeneic HCT still provides an opportunity for long-term survival for certain patients with relapsed APL for whom autologous HCT is unlikely to be effective. The dismal outcome of those with prior autologous HCT who underwent allogeneic HCT in non-CR poses a significant therapeutic challenge.