Fludarabine Based Conditioning for Allogeneic Transplantation in Severe Aplastic Anemia.

Patients with severe aplastic anemia (SAA) who are multiply transfused or septic have a poor outcome after allogeneic stem cell transplantation. Forty three patients (31 males and 12 females) with SAA underwent allogeneic BMT using a fludarabine based conditioning regimen between 1998 and 2005. The median age was 20 years (range: 4–38) with 11 children and 32 adults. All donors were 6 antigen matched HLA identical sibling or family donors. Co morbidities seen included bacterial sepsis in 15 patients, fungal pneumonia in 4 and a recent intracranial bleed in 5 patients. Seven patients had failed Antithymocyte or antilymphocyte globulin (ATG/ALG) and two patients had failed their first transplant. The median time from diagnosis to transplant was 12 months (range: 2 – 96) and the median transfusions prior to BMT was 28 (range: 2 – 380). Conditioning therapy consisted of: Fludarabine (Flu) 180 mg/m² over 6d + Busulfan (Bu) 8 mg/kg over 2d + ATG 40 mg/kg/day over 4 d in 17 patients, Flu 180 mg/m² over 6d + Cyclophosphamide (Cy) 120 mg/kg over 2d ± ATG 40 mg/kg/day over 4d in 17 patients, Flu/TBI/OKT3 in 4, and Cy 120 + Flu 150mg/m² in 5 patients. Graft versus host disease (GVHD) prophylaxis consisted of Cyclosporine and mini methotrexate. Graft source was peripheral blood stem cells in 39 patients and G-CSF stimulated bone marrow in 4. The median cell dose was 5.2 x 10⁸ MNC/kg (range: 2.1 – 13.6) for PBSC and 5.2 x 10⁸ TNC/kg (range: 3.7 – 6.8) for bone marrow. Five patients expired within the first 10 days due to sepsis. Thirty seven patients engrafted with a mean time to ANC > 500 of 11.6 days (range: 8 – 18) and median platelet engraftment time of 13 days (range: 8 – 32). One patient had primary graft failure and expired on day 64 due to fungal pneumonia despite a second transplant. Acute GVHD was seen in 14 patients (38%) with Grade III–IV GVHD in 4 (10.5%). Chronic GVHD was seen in 10 patients with 6 having limited and 4 with extensive GVHD. Two patients had secondary graft rejection on day + 24 and +60 respectively and expired due to fungal pneumonia. At a median follow up of 17 months (range: 5 – 78); 29 patients (67.7%) are alive and well. Among patients treated with Flu/Bu/ATG, 12/17 (70.5%) are alive and well while the DFS is 82% (14/17) in patients treated with Flu/Cy ± ATG. Comparison with patients conditioned with Cy/ATG during 1990–2004 is given in the table. This comparison suggests that a fludarabine based conditioning regimen may be better, with less rejection, than Cy/ATG for allogeneic BMT in sick patients with SAA who are infected and multiply transfused at the time of BMT.