Does the hematopoietic cell transplantation specific comorbidity index (HCT-CI) predict transplantation outcomes? A Prospective multicenter validation study of the kanto study group for cell therapy

Recent advances in allogeneic hematopoietic stem cell transplantation have led to increasing use of this modality in older patients who tend to have been more heavily pretreated and have more comorbidities. Thus, the evaluation of comorbidity is of increasing importance to more precisely assess the benefits and risks of the transplantation procedure. Researchers from Seattle developed the hematopoietic cell transplantation-specific comorbidity index (HCT-CI), which was associated with the risk of mortality in several retrospective studies. However, its clinical utility has not been extensively documented in prospective studies. The aim of the present study was to evaluate the utility of the HCT-CI prospectively in a multicenter setting. Overall survival (OS) and nonrelapse mortality (NRM) at 2years were 59% and 20%, respectively (n=243). We found that the HCT-CI in its original scale failed to predict OS and NRM in this set of patients. Thus, we applied a flexible HCT-CI risk scoring system (restratifying scores from 0 to 3 to indicate low risk, and scores of 4 or higher as high-risk). The flexible HCT-CI was found to predict 2-year NRM and OS better than the original HCT-CI (NRM: P=01, OS: P=003). In subgroup analysis, we evaluated the usefulness of the original HCT-CI for patients excluding those who received cord blood transplantation (n=186). Both 2-year OS and 2-year NRM were not significantly different according to the original HCT-CI (P=304, P=996), but with the flexible HCT-CI, there were significant differences in 2-year OS and 2-year NRM (P=005 and P=005, respectively). Multivariate analysis identified age >50, performance status (PS) <90, donor type (HLA-mismatched/unrelated donor), and the flexible HCT-CI ≥4 as significant predictors for worse OS at 2years. However, the flexible HCT-CI did not remain a significant predictor for NRM at 2years in multivariate analysis, whereas age, PS, and donor type did. The HCT-CI did not consistently predict both NRM and OS, but it still can be a useful tool in combination with other factors, such as PS and age. Furthermore, the HCT-CI, although potentially useful for capturing pretransplantation comorbidity and risk assessment, may need further validation before its adoption for routine clinical use.