Favorable Resuls After Primed G-CSF BMT (G-BMT) for Patients (pts) with Severe Aplastic Anemia (SAA) Conditioning with Buslfan (Bu), Cyclophosphamide (Cy) and Rabbit ATG Using Mycophenolate Mofetil (MMF) and Cyclosporine-A (CSA) for Gvhd Prophylaxis: Rapid Neutrophil Engraftment, Low Rejection Rate and Chronic Gvhd.

Abstract 1279

Patients (pts) with SAA in Brazil, in general, receive multiple transfusions and prolonged immunosuppresion with steroids and/ or cyclosporine (CSA) prior to be referred to allo-SCT. Therefore the rate of early and late graft rejection and infectious complications are high in this population.

G-BMT has shown to accelerate neutrophil recovery after allo-BMT from HLA-matched related donor (Ostronoff, M. et al. Biol Blood Marrow Transplant 2006; 12:729-33). Conditioning regimen using Bu/ Cy for SAA has been shown to decrease graft rejection after allo-BMT in pts who received multiple transfusions (Duley et al. Bone Marrow Transplant. 2004;33:9-13). To faster the neutrophil recovery and reduce the incidence of graft rejection, we used G-BMT from matched related donor to treat 22 polytransfused pts with SAA after conditioning with Bu/Cy. In addition, we incorporated ATG to our conditioning regimen to reduce both GVHD and graft rejection.

From May 2005, 45 pts with SAA underwent HLA matched-related G-BMT at our center. Median age was 21 years (3 - 56 yrs). Conditioning consisted of Bu 4mg/kg on D-6, Cy 50mg/kg/day (D-5 to D-2) and rabbit-ATG 3.75mg/kg/day (D-3 to D-1). GVHD prophylaxis consisted of CSA and MMF.

The donors received G-CSF 5 μg/kg/d SC for 5 days before bone marrow harvest (day –4 to day 0). Median CD34+, CD3+ and CD8+ cell count was respectively 3.7 × 10⁶ cells/ kg (1.2 - 10.3), 36 × 10⁶cells/kg (17 - 62) and 15 × 10⁶ cells/kg (8 - 40). All pts received G-CSF 10 micrograms/kg/day SC from D+1 until neutrophil engraftment.

The protocol was approved by our institutional review board and informed consent was obtained from each patient and donor and or their guardians.

Median time to neutrophil (ANC> 500/mm3) and platelets (>20,000/mm3) engraftment were 10 days (5 - 16 d) and 19 days (18 - 34 d), respectively.

There were 6 episodes of serum-sickness; 1 pt developed tuberculosis pneumonia which was successfully treated with anti-mycobacterium; 9 pts (20%) developed BK-associated hemorrhagic cystitis which resolved after hyper-hydration and leflunomide. One more severe case of cystitis were treated in association with cidofovir. Positive CMV-antigeneima (≥ 2 cells) occurred in 17pts (38%) and only 1 pt had CT scan changes suggestive of CMV pneumonia. All these pts were successfully treated with gancyclovir.

Grade ≥ II acute GVHD occurred in 15 pts (33%) and grade III-IV in 4 (9%); extensive and localized chronic GVHD occurred in 2 (5%) and 3 pts (7%), respectively.

Five pts died. Causes of death included 4 cases of acute GVHD, 1 aspergilosis that was likely acquired prior to transplant in a patient with prolonged leukopenia and who was on chronic steroids for 4 years. OS was 90% with a median follow up of 24 months (6-60 mo).

G-BMT after conditioning with Bu, Cy and rabbit-ATG for pts with SAA with history of prolonged use of immunosuppressants and multiple transfusions prior to transplant resulted in rapid neutrophil engraftment with low incidence of graft rejection and chronic GVHD. Infectious complications, especially viral, were frequent; therefore diligent surveillance for infectious process in this patient population is warranted.