Treatment of aplastic anemia

Survival of patients with aplastic anemia after immunosuppressive therapy with ATG/ALG ranges from 35% to 60%. However, long-term follow-up on these patients has indicated a high frequency of hematologic complications, including PNH, myelodysplasia, ANL, and recurrent aplasia. In contrast to immunosuppressive therapy, allogeneic marrow transplantation results in cure of aplasia. Problems initially limiting the success of HLA-matched allogeneic marrow transplants included graft rejection and complications associated with acute and chronic GVHD. Infusion of donor buffy coat cells along with marrow or alternatively more intensive immunosuppressive regimens containing irradiation have substantially decreased the risk of rejection. However, buffy coat infusion increases the incidence of chronic GVHD and irradiation treatment adds to toxicity of the conditioning regimen as well as producing long-term complications. The incidence and severity of acute GVHD have been significantly decreased by the use of MTX/CSP as GVHD prophylaxis; however, this regimen has had no impact on the incidence of chronic GVHD. Long-term survival in multiply transfused patients after HLA-identical marrow transplantation is on the order of 60% to 70%; survival in untransfused patients approximates 80%. Patients less than age 18 transplanted on protocols currently active in Seattle have greater than 90% survival. Further increases in survival must come from improvement in preventing and treating chronic GVHD. Patients diagnosed with aplastic anemia should have rapid HLA typing performed to identify possible marrow donors. Transfusions from prospective marrow donors should be avoided and the patient referred to a major treatment center. We continue to recommend allogeneic marrow transplantation for patients with severe aplastic anemia who are less than 40 years old and who have HLA-identical related donors. Immunosuppressive therapy should be tried first in patients without HLA-matched donors and for patients over the age of 40. HLA-mismatched marrow transplantation and use of unrelated marrow donors for severe aplastic anemia remain areas of active research.