Unrelated Donor Umbilical Cord Blood Transplantation in Pediatric Myelodysplastic Syndrome: A Single-Center Experience

Abstract 

Myelodysplastic syndromes (MDS) respond poorly to chemotherapy. Between 1995 and 2006, 23 pediatric patients with MDS were transplanted with unrelated donor umbilical cord blood (UUCB) at our center. The median age was 11.1 years (range: 1.1-19.7), median weight was 38.6 kg (range: 9.6-62.6), 61% of patients were male, and median time from diagnosis to transplant was 6.6 months (range: 2.0-61.4). Patients were followed for a median of 5.3 years (range: 1.6-12.4 years) posttransplant. MDS stage was refractory anemia (RA) in 12, refractory anemia with excess blasts (RAEB) in 8, and refractory anemia with excess blasts in transformation (RAEB-T) in 3 patients; 18 (78%) patients had primary MDS. Monosomy 7 was present in 17(74%) patients. Patients with acute myelogenous leukemia (AML) were excluded. Preparative regimen was total body irradiation (TBI) based in 18 (78%) patients. Graft-versus-host-disease (GVHD) prophylaxis was cyclosporine (CsA)/steroids (19 patients) or CsA/mycophenolate mofetil (MMF; 4 patients). Grafts were HLA matched at Class I (A and B) at low resolution and Class II (DRB1) at the allelic level, resulting in 16 (70%) 4/6 and 7 (30%) 5/6 matched transplants. The grafts contained a median of 4.0 × 10⁷ (range: 1.7-12.6) total nucleated cells (TNC)/kg precryopreservation; 3.6 × 10⁷ (range: 1.0-12.0) TNC/kg and 1.7 × 10⁵ (range: 0.2-28.5) CD34⁺ cells/kg were infused. Cumulative incidence of neutrophil engraftment (absolute neutrophil count [ANC] >500/μL) at day 42 and day 100 was 73.9% (95% confidence interval [CI] 55.1%-92.7%) and 91.3% (95% CI 71.3%-100.0%) respectively, and that of platelet engraftment (50 K) at 180 days was 69.6% (95% CI 49.8%-89.4%). Three patients had graft failure whereas 3 patients (13%) engrafted slowly (after day 42). Three patients developed acute GVHD (aGVHD) grades II-IV with a cumulative incidence at 100 days of 13% (95% CI 0.0%-27.1.0%). Four patients relapsed with a cumulative incidence of relapse at 3 years of 13.0% (95% CI 0.0%-27.1%). Cumulative incidence of nonrelapse mortality (NRM) at 1 year was 27% (95% CI 8.0%-46.0%). Ten patients died: 3 graft failure, 4 relapse, 2 infections (1 adenovirus, 1 toxoplasmosis), and 1 Epstein-Barr virus (EBV) lymphoproliferative disorder. Probabilities of event-free survival (EFS) at 1 and 3 years were 69.6% (95% CI 46.6%-84.2%) and 60.9% (95% CI 38.3%-77.4%), respectively. Factors associated with better EFS were age ≤11 years (P = .05) and weight ≤38 kg (P = .03). These results, especially in younger patients with monosomy 7 positive MDS, are equivalent to published matched allogeneic bone marrow data. UUCB should be actively considered for pediatric MDS patients lacking matched related or unrelated adult donors.

Key Words: MDS, Myelodysplastic syndrome, Unrelated umbilical cord blood transplantation, Allogeneic transplantation, Pediatric, Children