Outcome of Allogeneic Stem Cell Transplantation for Patients with Severe Aplastic Anemia after Conditioning with Procarbazine, ATG and Cyclophosphamide: A Single Center Experience.

Background: Cyclophosphamide (CY, 200 mg/kg) plus ATG seems to be accepted as a standard conditioning regimen in HLA-matched sibling stem cell transplantation (SCT) for severe aplastic anemia (SAA). We report herein the outcome of allogeneic SCT for the patients with SAA conditioned with procarbazine (PCB), ATG and CY.

Methods: Between January 1995 and March 2004, consecutive one hundred and sixty two patients with SAA received matched sibling SCT after conditioning with PCB, ATG and CY. The median age of patients was 28.5 (16~50) and median interval between diagnosis and SCT was 10.5 months (1~216). Fifty-five patients (34%) had a history of immunosuppressive therapy before SCT. The conditioning regimen consisted of PCB (6.25 mg/kg/day, 6 days), CY (50 mg/kg/day, 4 days) and ATG (1.25 mg/kg/day, 3 days). No graft manipulation was performed in 92 patients (52%), and donor marrow expansion and megadose transplantation (bone marrow plus CD34⁺ isolated PB as a stem cell source) were done in 35 patients (21.6%). All patients received of cyclosporine and methotrexate as GVHD prophylaxis.

Results: The median dose of CD34⁺ and CD3⁺ cells infused were 4.8 x 10⁶/kg (0.8~49.6) and 5.1 x 10⁷/kg (0 ~ 38), respectively. Median time to neutrophil recovery more than 500/μL and platelet recovery more than 20,000/μL were 13 days (0~49) and 19 days (0~150), respectively. All patients achieved successful primary engraftment, but delayed engraftment failure developed in 18 patients (11%). Ten among 18 patients who developed graft failure received second SCT, resulting survival of 9 patients. The incidence of acute (more than grade II) and chronic GVHD were 9.3% (n=15) and 13.0 % (n=21), respectively. DFS and overall survival (OS) at 6 years was also 90%. Factors influencing on DFS on univariate analysis were patient and donor’s age, development of acute and chronic GVHD, and times of pregnancy (over 2 times). Development of acute and chronic GVHD, and occurrence of rejection were factors that influence DFS on multivariate analysis. Causes of death (n=15) were pneumonia (n=4), rejection (n=4), GVHD±infection (n=2), chronic GVHD (n=1), MOF (n=1), CVA (n=1), autoimmune hemolytic anemia (n=1), and unknown (n=1).

Conclusions: These data suggest that the conditioning regimen used in this study is feasible for patients with SAA who received matched sibling SCT. GVHD and rejection were the most important factors that influence DFS.