Extramedullary relapses after allogeneic stem cell transplantation for acute myeloid leukemia: clinical characteristics, incidence, risk factors and outcomes.

Acute myeloid leukemia (AML) relapse after allogeneic hematopoietic cell transplant (allo-HCT) is challenging. Data on extramedullary relapse (EMR) after allo-HCT are limited. We analyzed 215 patients with AML who underwent allo-HCT in our institution between January 2005 and December 2015. We limited this retrospective review to patients who received a MA conditioning, were in complete remission (CR) at the time of transplant and who received a matched sibling transplant, all other patients were excluded to avoid heterogeneity. Seventy-seven (35.8%) patients experienced disease relapse, 45 had BMR, and 32 had EMR. The only variable that was statistically associated with EMR post allo-HCT was male sex (OR = 3.2 (1.2, 8.2), p-value = 0.01); there was a trend for association between transplant in >CR2 and EMR (OR = 0.38 (0.14, 1.06), p-value = 0.06). The median overall survival (OS) after relapse for all relapses was 10 months (95% CI 4.839-15.161). The median OS for BMR group was 8 months (95% CI 2.850-13.150) and 14 months for the EMR group (95% CI 5.776-22.224); however, this was not statistically significant, p-value = 0.4. Multivariate analysis revealed that gender, treatment modality, and time from allo-HCT to relapse (≥12 vs. <12 months) have significant association with the post-relapse death. Male gender was the only significant factor associated with EMR.