Influence of recipient's Age On the Outcome of HLA-Matched Sibling Transplants in Adult Patients with Severe Aplastic Anemia Who Conditioned with Fludarabine-Based Regimen

There is a controversy concerning upper age limit of recipient in allogeneic stem cell transplantation (allo-SCT) of severe aplastic anemia (SAA) because older patients have an increased risk of transplant-related mortality (TRM). Recently, a less toxic regimen comprising reduced dose of cyclophosphamide (CY), fludarabine (Flu), and ATG (Flu/CY/ATG) was introduced for conditioning the patients with SAA scheduled for HLA-identical sibling allo-SCT. We analyzed the outcome of these patients after conditioning with Flu/CY/ATG regimen according to recipient's age.

We analyzed 82 consecutive adult patients transplanted from March 2002 to June 2011, followed conditioning with CY (50 mg/kg/day × 2 days), Flu (30 mg/m²/day × 6 days), and ATG (2.5 mg/kg/day × 4 days).

The median age of patients was 39 years (range, 13–58 years). 29 (35.4%) patients were very SAA at the time of allo-SCT. Stem cell sources were bone marrow (BM, n=59), peripheral blood stem cell (PBSC, n=12), and BM+PBSC (CD34⁺ cell selection, n=11). The conditioning regimen was well tolerated, with low TRM (4.9%). Neutrophil engraftment was observed in all patients; the median time to engraftment of neutrophils and platelets was 12 and 17 days, respectively. The 100-day cumulative incidence (CI) of acute graft-versus-host disease (GVHD, grade °Ã2) was 3.7% and 2-year CI of chronic GVHD was 4.4%. With a median follow-up of 3 years, overall survival (OS) and failure-free survival was 93% and 83%, respectively. Seven patients (8.5%) developed delayed graft failure and 6 patients of them have successful durable engraftment after second allo-SCT without TRM. Seven patients died of veno-occlusive disease (n=1), cytomegalovirus pneumonia (n=2), sepsis (n=2), clonal evolution after allo-SCT (n=2, 1 acute myeloid leukemia and 1 myelodysplastic syndrome), respectively. 3-year probability of OS by age group were 88% at less than 20 years old (n=8), 97% at 20–39 (n=34), 92% at 40–49 (n=26), 86% at 50–59 (n=14). There is no significant difference in OS according to age group (p=0.426).

These data indicate that the Flu/CY/ATG conditioning regimen is well tolerable with low TRM and CI of GVHD in all age group. Similar OS according to 4-divided age group suggest that patient's age more than 50 years old might be possible candidate for allo-SCT in SAA with Flu/CY/ATG conditioning regimen.

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No relevant conflicts of interest to declare.