Standard treatment of acquired SAA in adult patients 18–40 years old with an HLA-identical sibling donor

We analyzed the outcome of 692 patients with severe aplastic anemia (SAA) receiving transplants from HLA-matched siblings. A total of 134 grafts were peripheral blood progenitor cell (PBPC) grafts, and 558 were bone marrow (BM) grafts. Rates of hematopoietic recovery and grades 2 to 4 chronic graft-versus-host disease (GVHD) were similar after PBPC and BM transplantations regardless of age at transplantation. In patients older than 20 years, chronic GVHD and overall mortality rates were similar after PBPC and BM transplantations. In patients younger than 20 years, rates of chronic GVHD (relative risk [RR] 2.82; P = .002) and overall mortality (RR 2.04; P = .024) were higher after transplantation of PBPCs than after transplantation of BM. In younger patients, the 5-year probabilities of overall survival were 73% and 85% after PBPC and BM transplantations, respectively. Corresponding probabilities for older patients were 52% and 64%. These data indicate that BM grafts are preferred to PBPC grafts in young patients undergoing HLA-matched sibling donor transplantation for SAA.

Bone marrow has been shown to be superior to peripheral blood, as a stem cell source, in young patients (<20 years of age) with acquired aplastic anemia undergoing a matched sibling transplant. The aim of this study was to test whether this currently also holds true for older patients with acquired aplastic anemia. We analyzed 1886 patients with acquired aplastic anemia who received a first transplant from a human leukocyte antigen identical sibling between 1999 and 2009, with either bone marrow (n=1163) or peripheral blood (n=723) as the source of stem cells. In multivariate Cox analysis negative predictors for survival were: patient's age over 20 years (RR 2.0, P<0.0001), an interval between diagnosis and transplantation of more than 114 days (RR 1.3, P=0.006), no anti-thymocyte globulin in the conditioning (RR 1.6, P=0.0001), a conditioning regimen other than cyclophosphamide (RR=1.3, P=0.008) and the use of peripheral blood as the source of stem cells (RR 1.6, P<0.00001). The survival advantage for recipients of bone marrow rather than peripheral blood was statistically significant in patients aged 1-19 years (90% versus 76% P<0.00001) as well as in patients aged over 20 years (74% versus 64%, P=0.001). The advantage for recipients of bone marrow over peripheral blood was maintained above the age of 50 years (69% versus 39%, P=0.01). Acute and chronic graft-versus-host disease were more frequent in peripheral blood transplants. Major causes of death were graft-versus-host disease (2% versus 6% in bone marrow and peripheral blood recipients, respectively), infections (6% versus 13%), and graft rejection (1.5% versus 2.5%). This study shows that bone marrow should be the preferred stem cell source for matched sibling transplants in acquired aplastic anemia, in patients of all age groups.

The addition of antithymocyte globulin (ATG) to a regimen of high-dose cyclophosphamide has been advocated to enhance engraftment after allogeneic bone marrow transplantation (BMT) for severe aplastic anemia (SAA). In a prospective clinical trial, 134 patients were randomly assigned to receive cyclophosphamide alone or in combination with ATG. All patients received T-cell-replete bone marrow from an HLA-matched sibling. With a median follow-up of 6 years, the 5-year probabilities of survival were 74% for the cyclophosphamide alone group and 80% for the cyclophosphamide plus ATG group (P = .44). Graft failure and graft-versus-host disease (GVHD) rates were similar in both groups. With the survival rates achieved, this study is not adequately powered to detect significant differences between the 2 treatment groups. In conclusion, the results of allogeneic BMT for SAA have improved over time related to advances in supportive care. The addition of ATG to the preparative regimen did not significantly improve the outcome.