Comparison of Outcomes Between Unrelated Donor and Sibling Donor Transplant in Adult Patients with Severe Aplastic Anemia: A Single Center Retrospective Study

Abstract 4151

For the patient with severe aplastic anemia (SAA) who do not have a sibling donor and had failed to immunosuppressive therapy, allogeneic stem cell transplantation (SCT) from an unrelated donor is therapeutic option. Although unrelated SCT (u-SCT) has shown less favorable outcomes, there were few studies comparing unrelated donor to sibling donor transplant. The aim of the present study was to evaluate the feasibility of u-SCT in adult SAA patients compared with sibling SCT (s-SCT).

This study examined 157 consecutive patients who underwent allogeneic SCT at our institution between April 2001 and December 2011. In this study, for a homogenous cohort, patients who received second allogeneic SCT were excluded. The diagnosis of acute GVHD or chronic GVHD was made as the NIH published consensus criteria.

There were 71 male and 86 female patients with a median age of 31 years (range, 13–59 years). The median interval from the diagnosis to transplantation was 24 months (range; 1–346 months). The median transfusions prior to SCT were 47 units (range; 4–680 units). Patients with SAA (n=114) or VSAA (n=43) had received SCT from sibling donor (n=82) or unrelated donor (n=75). The conditioning regimen for s-SCT consisted of fludarabine (180 mg/m²) + cyclophosphamide (CY, 100 mg/kg) + ATG (10 mg/kg), and the conditioning regimen for u-SCT consisted of TBI (fractionated, 800 cGy) + CY (100–120 mg/kg) ± ATG (2.5 mg/kg) (Lee JW, et al, Biol BMT 2011, 17:101). GVHD prophylaxis consisted of CsA + MTX in s-SCT and FK506 + mini-MTX in u-SCT, respectively. After a median follow-up of 45 and 50 months for s-SCT and u-SCT, respectively, the 3-year estimated OS rates were 92.7 and 89 % for s-SCT and u-SCT (P=0.650), respectively. 15 patients (7 in s-SCT, 8 in u-SCT) died of transplant toxicities, including in s-SCT, acute GVHD (n=1), infections (n=4), and occurrence of MDS or AML (n=2) and in u-SCT, acute GVHD (n=4), chronic GVHD (n=1), infection (n=1), thrombotic microangiopathy (n=1). Nine patients (8 in s-SCT, 1 in u-SCT) developed secondary engraftment failure. The cumulative incidence of acute GVHD (≥grade II) was 4.9% in s-SCT and 44.0% in u-SCT (P<0.001). The cumulative incidence of chronic GVHD also showed higher in u-SCT than s-SCT (4.2% vs 44.4%, P<0.001).

This study showed that survival of u-SCT is comparable to that of s-SCT. Therefore, early application of u-SCT should be considered in patients with SAA/VSAA in case of availability of well matched donor. Because the incidence of GVHD is significantly higher in u-SCT than s-SCT, further study is mandatory to reduce the incidence of GVHD in u-SCT setting.