Comparison of two pretransplant predictive models and a flexible HCT-CI using different cut off points to determine low-, intermediate-, and high-risk groups: the flexible HCT-CI Is the best predictor of NRM and OS in a population of patients undergoing allo-RIC

Abstract

Patient comorbidities are being increasingly analyzed as predictors for outcome after hematopoietic stem cell transplantation (HSCT), especially in allogeneic HSCT (Allo-HSCT). Researchers from Seattle have recently developed several pretransplant scoring systems (hematopoietic cell transplantation comorbidity index [HCT-CI] and the Pretransplantation Assessment of Mortality (PAM) model) from large sets of HSCT recipients with the aim of improving non-transplant models, mainly the Charlson Comorbidity Index (CCI). The validation of these comorbidity indexes in other institutions and in different disease and conditioning-related settings is of interest to determine whether these models are potentially applicable in clinical practice and in research settings. We performed a retrospective study in our institution including 194 consecutive reduced-intensity conditioning (RIC) AlloHSCT (allo-RIC) recipients to compare the predictive value of the PAM score, CCI, the original HCT-CI, and the flexible HCT-CI using a different risk group stratification. The median patient pretransplant scores for the HCT-CI, PAM, and CCI were 3.5, 22, and 0, respectively. The flexible HCT-CI risk-scoring system (restratified as: low risk [LR] 0-3 points, intermediate risk [IR] 4-5 points, and high risk [HR] >5 points) was the best predictor for non-relapse mortality (NRM). The 100-day and 2-year NRM incidence in these risk categories was 4% (95% confidence interval C.I. 2%-11%), 16% (95% C.I. 9%-31%), and 29% (95% C.I. 19%-45%), respectively (P < .001), and 19% (95% C.I. 12%-28%), 33% (95% C.I. 22%-49%), and 40% (95% C.I. 28%-56%), respectively (P=.01). However, we found no predictive value for NRM using neither the original HCT-CI nor the PAM or CCI models. The better predictive capacity for NRM of the flexible HCT-CI than PAM and CCI was confirmed with the c-statistics (c-statistics of 0.672, 0.634, and 0.595, respectively). Regarding the 2-year overall survival (OS), the flexible HCT-CI score categories were also associated with the highest predictive HR. In conclusion, our single-center study suggests that the flexible HCT-CI is a good predictor of 2-year NRM and survival after an allo-RIC.