Unrelated cord blood transplantation in adult and pediatric acute lymphoblastic leukemia: effect of minimal residual disease on relapse and survival.

Data on pretransplantation minimal residual disease (MRD) and outcomes of umbilical cord blood transplantation (UCBT) are limited. Out of the 143 patients with acute lymphoblastic leukemia (ALL) who underwent UCBT at the University of Minnesota between 2004 and 2010, we evaluated 86 patients with available MRD assessment data by 4- and 8-color flow cytometry analysis immediately before transplantation. Ten patients (11.6%) were MRD-positive, and 76 were MRD-negative (88.4%). Most of the patients (82%) received myeloablative conditioning. GVHD prophylaxis consisted of cyclosporine and mycophenolate mofetil. In multivariate analysis, age, disease status (complete remission [CR] 1 versus CR2/CR3), disease group (precursor B cell ALL versus Philadelphia chromosome-positive ALL versus T cell ALL), and time to transplantation had no impact on relapse. Patients with MRD before UCBT had a greater incidence of relapse at 2 years (relapse rate, 30%; 95% confidence interval [CI], 4%-56%) and lower 3-year disease-free survival (30%; 95% CI, 7%-58%) compared with those without MRD (relapse rate, 16%; 95% CI, 8%-25%; P = .05; disease-free survival, 55%; 95% CI, 43%-66%; P = .02). Our data suggest that in patients with ALL, achieving an MRD-negative state before UCBT improves outcomes.