Influence of Nucleated Cell Dose on Overall Survival of Unrelated Cord Blood Transplantation for Patients with Severe Acquired Aplastic Anemia: A Study by Eurocord and the Aplastic Anemia Working Party of the European Group for Blood and Marrow Transplant

Information is scarce on outcomes after unrelated cord blood transplantation (UCBT) for patients with severe aplastic anemia (SAA). We retrospectively analyzed 71 patients (median age, 13 years; 28 adults) with SAA (9 with paroxysmal nocturnal hemoglobinuria [PNH]) who received a single-unit (n = 57; 79%) or double-unit UCBT (n = 14; 19%) in 32 centers between 1996 and 2009. A reduced-intensity conditioning regimen was provided in 68% of the patients. The cumulative incidence (CI) of neutrophil recovery was 51% ± 6% at day 60, with significantly better engraftment seen in recipients of higher prefreezing total nucleated cell (TNC) dose (>3.9 107/kg; hazard ratio [HR], 1.5; P = .05). The CI of platelet engraftment at day 180 posttransplantation was 37% ± 7%, that of grade II-IV acute GVHD was 20% ± 5%, and that of chronic GVHD at 3 years was 18% ± 5%. At a median follow-up of 35 months (range, 3-83 months), the estimated probability of 3-year overall survival (OS) was 38% ± 6%. Significantly improved OS was seen in recipients of >3.9 107 TNCs/kg prefreezing (45%, compared with 18% for recipients of ≤3.9 107 TNC/kg; HR, 0.4; P = .007). These results highlight the fundamental role of cell dose for both engraftment and OS in patients with SAA undergoing UCBT.