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 a

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 nontransplant 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 nonreplapse 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.