Impact of age on outcomes after bone marrow transplantation for acquired aplastic anemia using HLA-matched sibling donors

Background Transplantation from an HLA-matched sibling is the treatment of choice for young patients with acquired severe aplastic anemia. For older patients, the acceptable upper age limit for transplantation as first-line treatment varies. The current analysis, therefore, sought to identify age or ages at transplantation at which survival differed. Design and Methods We studied the effect of patients' age, adjusting for other significant factors affecting outcomes, in 1307 patients with severe aplastic anemia after HLA-matched sibling transplantation using logistic and Cox regression analysis. Age categories (< 20 years, 20-40 years, > 40 years) were determined using Martingale residual plots for overall survival and categories based on differences in survival. Results Patients aged over 40 years old were more likely to have had immunosuppressive therapy, a poor performance score and a longer interval between diagnosis and transplantation. Neutrophil recovery was similar in all age groups but patients aged over 40 years had a lower likelihood of platelet recovery compared to patients aged less than 20 years (OR 0.45, P=0.01) but not compared to those aged 20-40 years (OR 0.60, P=0.10). Compared to the risk of mortality in patients aged less than 20 years, mortality risks were higher in patients over 40 years old (RR 2.70, P < 0.0001) and in those aged 20-40 years (RR 1.69, P < 0.0001). The mortality risk was also higher in patients aged over 40 years than in those 20-40 years old (RR 1.60, P=0.008). Conclusions Mortality risks increased with age. Risks were also higher in patients with a poor performance score and when the interval between diagnosis and transplantation was longer than 3 months, implying earlier referral would be appropriate when this treatment option is being considered.