Pre- and post-transplant extramedullary involvement in adult patients with t(8;21)(q22;q22) acute myeloid leukemia: incidence, risk factors and outcomes

The risk factors and prognostic impact of extramedullary involvement (EMI) before and after allogeneic hematopoietic stem-cell transplantation (allo-HSCT) in t(8;21)(q22;q22) acute myeloid leukemia (AML) remain inconclusive. We performed a multicenter retrospective study including 560 t(8;21) AML patients from 15 Chinese hematology centers. <i>KIT</i> mutations were more frequently observed in patients with EMI at diagnosis. EMI at diagnosis was not an independent risk factor for overall survival (OS) after adjustment for <i>KIT</i> mutations. The 3-year post-transplant OS rates between isolated extramedullary relapse (EMR) and bone marrow relapse after allo-HSCT were comparable. Chronic graft-versus-host disease (cGVHD) was associated with increased incidence of isolated EMR (HR = 2.33, <i>p</i> = 0.048). Pre- and post-transplant minimal residual disease (MRD), measured by <i>RUNX1-RUNX1T1</i> transcript levels, showed no significant association with isolated EMR. In conclusion, EMI at diagnosis may not significantly impact survival in t(8;21) AML. For patients with cGVHD after allo-HSCT, EMR should be monitored.