Conditional Survival, Cause-Specific Mortality, and Risk Factors of Late Mortality After Allogeneic Hematopoietic Cell Transplantation

Abstract

Long-term mortality after hematopoietic cell transplantation (HCT) is conventionally calculated from the time of HCT, ignoring temporal changes in survivors’ mortality risks. Conditional survival rates, accounting for time already survived, are relevant for optimal delivery of survivorship care but have not been widely quantified. We estimated conditional survival by elapsed survival time in allogeneic HCT patients and examined cause-specific mortality. We calculated conditional survival rates and standardized mortality ratio for overall and cause-specific mortality in 4485 patients who underwent HCT for malignant hematologic diseases at a large transplant center during 1976–2014. Statistical tests were two-sided. The 5-year survival rate from HCT was 48.6%. After surviving 1, 2, 5, 10, and 15 years, the subsequent 5-year survival rates were 71.2%, 78.7%, 87.4%, 93.5%, and 86.2%, respectively. The standardized mortality ratio was 30.3 (95% confidence interval [CI] = 29.2 to 35.5). Although the standardized mortality ratio declined in longer surviving patients, it was still elevated by 3.6-fold in survivors of 15 years or more (95% CI = 3.0 to 4.1). Primary disease accounted for 50% of deaths in the overall cohort and only 10% in 15-year survivors; the leading causes of nondisease-related mortality were subsequent malignancy (26.1%) and cardiopulmonary diseases (20.2%). We also identified the risk factors for nondisease-related mortality in 1- and 5-year survivors. Survival probability improves the longer patients survive after HCT. However, HCT recipients surviving 15 years or more remain at elevated mortality risk, largely because of health conditions other than their primary disease. Our study findings help inform preventive and interventional strategies to improve long-term outcomes after allogeneic HCT.