Prevalence of extramedullary relapses is higher after allogeneic stem cell transplantation than after chemotherapy in adult patients with acute myeloid leukemia.

Although studies have demonstrated a high prevalence of extramedullary (EM) relapse after allogeneic stem cell transplantation (allo-SCT) in patients with acute myeloid leukemia (AML), the prevalence of EM relapse has not been compared with that after chemotherapy. This study investigated the prevalence of EM relapse among 498 adult AML patients (median age, 57 years; range, 15-82 years) who underwent intensive chemotherapy. A total of 281 relapses occurred in 210 patients (36 after allo-SCT; 245 after chemotherapy), and 33 relapses (11.7%) were accompanied by EM disease. Among these relapses, EM disease was more frequently observed at relapse after allo-SCT than after chemotherapy (25% vs. 9%, respectively; p=0.008). Eight of 33 relapses after the first allo-SCT had EM disease, and only presence of extensive chronic graft-versus-host disease (GVHD) was identified as a predisposing factor for EM relapse. Additionally, the 1-year overall survival rate after relapse was not significantly different when comparing those with EM relapse and those with BM relapse (38% vs. 16%, respectively; p=0.279). These data suggest that AML patients undergoing allo-SCT should be closely followed for signs of EM relapse, especially those with extensive chronic GVHD.