Outcomes of 40 Adult Patients after Double Cord Blood Transplantation Using a Reduced Intensity Chemotherapy Conditioning Regimen.

Umbilical cord blood is an alternative stem cell source for patients without matched related or unrelated donors. However, single cord blood unit transplantation in adults is associated with high transplant related mortality, mostly due to infection. In this study, we used a reduced intensity conditioning regimen followed by infusion of two partially matched cord blood units. The conditioning regimen was fludarabine 30mg/m²/day Days -8,-7,-6,-5,-4,-3 (total dose 180mg/m²), melphalan 100mg/m²/day Day -2, and rabbit antithymocyte globulin (thymoglobulin) 1.5 mg/kg/day Days -7,-5,-3,-1 (total dose 6.0 mg/kg). Cord blood units were a 4/6 or better HLA A, B, DR match with each other and with the patient, and contained a minimum combined pre-freeze cell dose of 3.7 x 10⁷NC/kg. GVHD prophylaxis was cyclosporine and mycophenolate mofetil, for the first 21 patients, and tacrolimus and sirolimus for the second cohort of 19 patients. Forty patients, 22 males (55%) and 18 females (45%) with a median age of 48 years (range 19–64 years) were treated. The diagnoses were AML (n=14), ALL (n=1), NHL (n=10), CLL (n=2), MDS (n=5), Hodgkins Disease (n=5), aplastic anemia (n=2), and chronic myelogeneous leukemia (n=1). Thirty-five patients have greater than 100 days of follow-up and are included in this analysis. The cell doses infused were a median of 4.0 x 10 ⁷NC/kg (range 3.0–6.7 x 10⁷) and 1.9 x 10 ⁵ CD34+ cells/kg (range 0.5–10.0 x 10⁵). Two patients (both with MDS complicating aplastic anemia) experienced primary graft failure, and received second cord blood transplants using a different conditioning regimen. Among the remaining patients, the median time to an absolute neutrophil count >500 was 21 days (range 14–70 days). There were two late graft failures. The median time to a platelet count >20,000 unsupported was 43 days (range 21–125 days). The incidence of acute GVHD Grades II–IV was 40% for the patients receiving cyclosporine/MMF and 29% for patients receiving tacrolimus and sirolimus. There were no deaths from acute GVHD in the cyclosporine/MMF group and one death from acute GVHD in the tacrolimus/sirolimus group. Seven patients (20%) developed chronic GVHD. The 100-day transplant related mortality was 14%. Two deaths were related to Epstein Barr virus related lymphoproliferative disorder, and the other deaths were due to a CNS bleed, staphylococcal sepsis, and respiratory failure due to aspergillus infection. Two patients have relapsed and one has progressive disease. With a median follow up of 14 months (range 3–31 months) the overall survival is 74% and the disease-free survival is 67%. Chimerism analysis showed predominance of one cord by Day +100. In 71% of patients, the first cord blood unit infused predominated. In conclusion,

1. engraftment of adult patients appears to be acceptable using double cord blood products and reduced intensity, non TBI conditioning regimen;

2. the risk of serious acute and chronic GVHD is low,

3. survival is excellent in a selected group of patients and

4. relapse rate is low, suggesting preservation of graft versus leukemia effect despite the low T cell dose.