Similar outcomes of alemtuzumab-based hematopoietic cell transplantation for SAA patients older or younger than 50 years.

Survival after allogeneic hematopoietic cell transplantation (HSCT) for severe aplastic anemia (SAA) among older patients remains poor and associated with increased risk for graft-versus-host disease (GVHD). In this retrospective study of 65 consecutive patients with acquired SAA who were transplanted using fludarabine, low-dose cyclophosphamide, and alemtuzumab (FCC), outcomes of 27 patients aged at least 50 years were compared with those of 38 patients younger than 50 years. The median age of the older cohort was 61 years (range, 51-71 years); 21 (78%) patients were transplanted from unrelated donors (3 of 21 from HLA 9/10 mismatch donors) and 6 from matched sibling donors. One-year GVHD-free, relapse-free survival (GRFS) was comparable to that of patients younger than 50 years (84% vs 94%, respectively; P = .23). Both groups showed low rates of acute (5% vs 4%) and chronic (18% vs 14%) GVHD, with no cases of severe GVHD among matched donor transplants, and similar 1-year transplant-related mortality (14% vs 5.4%, older vs younger; P = .23). HSCT comorbidity index (HTC-CI) scores were similar between the groups, but overall survival with an HCT-CI of at least 3 was lower compared with a score less than 3 (76% vs 98%; P = .005). Median donor T-cell chimerism among older patients was 64% and 60% at 1 and 3 years, respectively, and was similar to that of younger patients. Increased B regulatory cells potentially contributed to low alloreactivity and mutual donor-recipient tolerance in older patients. Effect of comorbidities rather than age alone may be a more important determinant of suitability for FCC HSCT in older patients.