Unrelated Umbilical Cord Blood Transplantation for Hematological Malignancies Using Fludarabine/BUCY2 Conditioning Regimen

Abstract 4572

Cord blood transplantation (CBT) is largely used to treat patients affected by hematological malignant disorders. Myeloablative TBI-based conditioning appears to provide reliable engraftment after CBT for malignancies. However, the toxicity of TBI limits their widespread use. So far, a standard non-TBI based regimen has not been firmly established. In order to overcome graft failure, we investigated a strategy using Fludarabine (FLU)/BUCY2 regimen in CBT for patients with hematologic malignancies. Seventeen patients(children 16, adult 1) with hematologic malignancies who underwent single-unit CBT used a conditioning regimen comprising FLU 120 ‡r/‡u, intravenous busulfan (BU) 12.8‡r/kg and cyclophosphamide (CY)120 mg/kg (FLU/BUCY2). All patients were given a combination of cyclosporine A and mycophenolate mofetil for graft-versus-host disease (GVHD) prophylaxis. Seventeen patients with acute leukemia (n=13), chronic myelogenous leukemia (n=4) were treated, thirteen of whom were high risk diseases and two were advanced-stage at CBT. Seventeen patients with a median age of 8 years (range,2.5–46 years) and a median weight of 32 kg (range, 12–55 kg)received the median number of nucleated cells and CD34⁺cells infused were 5.70× 10⁷/kg (range: 3.15–9.60×10⁷/kg) and 3.84× 10⁵/kg (range:1.27–5.24 ×10⁵/kg), respectively. The cumulative incidence of primary donor engraftment was 94% (16 patients); one patient had secondary graft failure. Median time to neutrophil≥0.5×10⁹/L was 17 days (range 12–30) and platelet engraftment (≥20×10⁹/L) was 35 days (range 14–56). Preengraftment syndrome (PES) developed in 71% of the patients at a median of 7days (range: 5–13).9 cases developed acute GVHD (56%), more than grade II in three cases. Two of fourteen patients who survived more than 100 days developed chronic GVHD. 12 cases are alive at a median follow-up of 7 months (range 3~ 11).The probability of overall survival at 100 days and 1 year are 88.2% and 67.9%, respectively. Two cases had extramedullary relapsed. Five cases died of severe GVHD (n=3), pulmonary toxicity (n=1) and secondary graft failure (n=1). Preliminary evidence of the small study suggests successful engraftment and decreasing relapse rate following FLU/BUCY2 regimen for CBT in patients with hematologic malignancies. But it had a tendency towards increasing the incidence of GVHD-related morbidity and mortality. Whether this regimen offers a survival benefit for patients with poor-risk leukemia has to be tested in larger prospective trials.