Long Term Outcome of Pediatric Patients with Severe Aplastic Anemia Treated with Anti-Thymocyte Globulin and Cyclosporine.

Acquired severe aplastic anemia (SAA) is a fatal bone marrow failure disorder which commonly affects the young. An increased incidence of SAA is observed in children and young adults between the ages of 15 and 25. In those who have a histocompatible sibling donor, hematopoietic stem cell transplantation (HSCT) is often performed; for the remainder of patients immunosuppressive therapy (IST) with an anti-thymocyte globulin (ATG) based regimen is the treatment of choice. The overall response rate (children + adults) to ATG is 60–70%, with prolonged survival achieved in 70–80% of cases. Most of the reports on the efficacy of IST with ATG in children are of small cohorts. Here we report the outcome of children under the age of 18 treated with horse ATG + cyclosporine (CsA) at our institution from 1989 to 2006. Overall 77 received horse ATG as the initial IST. The overall response rate at 6 months was 74% (57/77); the cumulative incidence of relapse at 10 years was 33% and the median time to relapse was 558 days. The cumulative incidence of evolution following IST was 8.5%; all 3 cases occurred among partial responders. Cytogenetic abnormalities that were detected after IST were: monosomy 7 in two patients and deletion 13q in one patient. Overall there were 13 deaths (17%): four occurred within the 3 months following IST in patients who had a pre-treatment ANC of less than 100/uL and nine deaths occurred further than 6 months of IST. The median time to death was 570 days. The overall 10-year survival for the entire cohort was 80%; long term survival in patients who responded to IST was 89%. We conducted a separate analysis in the age group of 18–21. In total, 35 patients in this age group were treated with h-ATG-based IST from 1989 to 2006. The overall hematologic response rate was 60% (21/35) of which 7 relapsed (33%). The overall response rate among children (< 18) was about 75% which is higher than what is observed in older patients at our institution (response rate of about 60%). The response rate in young adults approximates the overall adult response rate. The long term survival in pediatrics patients who respond to IST is very favorable at about 90%. IST remains a very good alternative in pediatric patients who lack an HLA-matched sibling donor and should be offered as initial therapy prior to an alternative HSCT.