Influence of comorbidities on outcome in 1102 patients with an allogeneic hematopoietic stem cell transplantation

The hematopoietic comorbidity risk index (HCT-CI) is a pre-transplant risk assessment tool used to qualify comorbidities to predict non-relapse mortality (NRM) of patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). HSCT procedures continue to improve. Therefore, the predictive value of HCT-CI needs to be re-evaluated. Our study is a retrospective analysis of pre-existing comorbidities assessing the relevance of the HCT-CI on the outcome of consecutive patients (n = 1102) undergoing allo-HSCT from 2006-2021. HCT-CI was classified as low (HCT-CI 0), intermediate (HCT-CI 1-2) and high-risk (HCT-CI ≥ 3). At 10 years, NRM for low, intermediate, and high-risk HCT-CI group was 21.0%, 26.0%, and 25.8% (p = 0.04). NRM difference was significant between low to intermediate (p < 0.001), but not between intermediate to high-risk HCT-CI (p = 0.22). Overall survival (OS) at 10 years differed significantly with 49.9%, 39.8%, and 31.1%, respectively (p < 0.001). In multivariate analysis of HCT-CI organ subgroups, cardiac disease was most strongly associated with NRM (HR = 1.73, p = 0.02) and OS (HR = 1.77, p < 0.001). All other individual organ comorbidities influenced NRM to a lesser extent. Further, donor (HR = 2.20, p < 0.001 for unrelated and HR = 2.17, p = 0.004 for mismatched related donor), disease status (HR = 1.41, p = 0.03 for advanced disease) and previous HSCT (HR = 1.55, p = 0.009) were associated with NRM. Improvement in transplant techniques and supportive care may have improved outcome with respect to comorbidities.