Isolated Extramedullary Relapse as a Poor Predictor of Survival after Allogeneic Hematopoietic Cell Transplantation for Acute Leukemia.

Limited and conflicting data exist on outcomes of patients with extramedullary relapses (EMRs) after allogeneic hematopoietic cell transplantation (allo-HCT) for acute leukemias. We retrospectively reviewed charts of consecutive allo-HCT recipients who underwent transplantation in our center with the indication of acute leukemia (July 1990 to July 2018). Incidences of isolated EMR (iEMR) and bone marrow relapse (BMR) were calculated using cumulative incidence (CI) analysis, with each and treatment-related mortality considered a competing risk. We studied 554 allo-HCT recipients for 1.8 years (range, .04 to 27.75). Ten-year CI of 10.5% for iEMR was associated only with advanced disease phase at transplantation, whereas 10-year CI of 34.8% for BMR was independently associated with pretransplant disease phase, lines of treatment, and fungal infections. Most iEMR and BMR patients (75% and 81%, respectively) received systemic treatment combined with local radiation for iEMR (26%) and donor lymphocyte infusions (16% and 28%, respectively) when feasible. Extensive chronic graft-versus-host disease (GVHD) was recorded in 47% of iEMR and 48% of BMR patients. Outcomes were poor both in iEMR (10-year overall survival [OS], 18.3%) and BMR (10-year OS, 19.1%). Independent predictors of OS were disease phase, type of donor, acute and chronic GVHD, fungal infections, iEMR, and BMR. In a large population with long-term follow-up, incidence of iEMR was relatively high, developed at the late post-transplant period, and was associated only with disease phase at transplantation. Furthermore, iEMR and BMR conferred similarly poor outcomes despite systemic treatment or extensive chronic GVHD.