Survival after response to immunosuppression in severe aplastic anemia. A large cohort (N = 243) of NIH patients who responded to treatment with the standard regimen of horse ATG plus cyclosporine was analyzed. Shown are long-term outcomes including the negative impact of a complicating event. Events were defined as relapse (need for further immunosuppression after protocol treatment) and clonal evolution (myelodysplasia/acute myeloid leukemia; almost always accompanied by a new cytogenetic abnormality in the BM). Approximately half of the patients did not experience a clonal event and poor survival was largely a consequence of disease progression. Data were censored for transplantation.¹