Allogeneic bone marrow transplantation for severe aplastic anemia: the Hong Kong scenario

Severe aplastic anemia (SAA) is a disease associated with high mortality. For young patients with HLA identical siblings, allogeneic bone marrow transplantation (BMT) offers the best chance of cure. Favourable results have also been reported using immunosuppressive therapy (IST). Transplantation is usually favoured for patients below 45 years of age. We report our experience of 11 allogeneic and one syngeneic BMT for adult Chinese patients with SAA, over a 4-year period from 1991 to 1995. Ten of the 12 (83 per cent) patients had received and failed prior IST including anti-thymocyte globulin (ATG) before being referred for BMT. Neutrophil and platelet engraftment was successful in 11 of them (92 per cent) and nine were completely transfusion independent after transplantation. Their overall 3-year survival was 67 per cent. The compromised overall result was due to a number of cases transplanted after a long time delay. No patient transplanted beyond 3 years from the initial time of diagnosis of SAA achieved long-term marrow engraftment, and they all eventually succumbed. On univariate analysis, a longer time delay and hence a larger amount of blood products exposure, were highly significantly statistically associated with inferior marrow engraftment and patient survival. Other factors including age, iron status, infused cell dose and the conditioning protocol were not found to significantly affect engraftment and survival. Graft versus host disease was clinically mild or absent in most patients. This may be related to ethnicity or previous ATG exposure. In conclusion, early allogeneic BMT was a safe and effective treatment in our small series of patients with SAA failing IST.