Validation of the Revised Pretransplant Assessment of Mortality Score in Patients with Acute Myelogenous Leukemia Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

The sum of the parts: what we can and cannot learn from comorbidity scores in allogeneic transplantation

Allogeneic hematopoietic cell transplantation (alloHCT) requires the comprehensive evaluation of patients across multiple dimensions. Among the factors considered, comorbidities hold great significance in the pretransplant assessment. As many as 40% of alloHCT recipients will have a high burden of comorbidities in contemporary cohorts. To ensure a standardized evaluation, several comorbidity scores have been developed; however, they exhibit variations in properties and performance. This review examines the strengths and weaknesses associated with these comorbidity scores, critically appraising these models and proposing a framework for their application in considering the alloHCT candidate. Furthermore, we introduce the concept that comorbidities may have specific effects depending on the chosen transplantation approach and outline the findings of key studies that consider the impact of individual comorbidities on alloHCT outcomes. We suggest that a personalized transplantation approach should not rely solely on the overall burden of comorbidities but should also take into account the individual comorbidities themselves, along with other patient, disease, and transplantation-related factors.

External Validation of the Revised Pretransplant Assessment of Mortality Score in Allogeneic Hematopoietic Cell Transplantation: A Cohort Study

Pretransplant risk scores such as the revised Pretransplant Assessment of Mortality (rPAM) score help to predict outcome of patients receiving allogeneic hematopoietic cell transplantation (allo-HCT). Since the rPAM has not been validated externally in a heterogeneous patient population with different diseases, we aimed to validate the rPAM score in a real-world cohort of allo-HCT patients. A total of 429 patients were included receiving their first allo-HCT from 2008 to 2015. The predictive capacity of the rPAM score for 4-year overall survival (OS), nonrelapse mortality (NRM), and cumulative incidence of relapse (CIR) after allo-HCT was evaluated. Moreover, we evaluated the impact of the rPAM score for OS and used uni- and multivariable analyses to identify patient- and transplant-related predictors for OS. In rPAM score categories of <17, 17–23, 24–30, and >30, the OS probability at 4 years differed significantly with 61%, 36%, 26%, and 10%, respectively (P < 0.0001). In contrast to CIR, the NRM increased significantly in patients with higher rPAM scores (P < 0.001). Regarding the OS, the rPAM score had an area under the receiver operating characteristics curve of 0.676 (95% confidence interval [CI], 0.625-0.727) at 4 years. In the multivariable analysis, the rPAM score was associated with OS—independently of conditioning regimens (adjusted hazard ratio per 1-unit increase, 1.10; 95% CI, 1.06-1.10; P < 0.001). Additionally, forced expiratory volume in 1 second and the disease risk index were the components of the rPAM significantly associated with outcome. In our large real-world cohort with extended follow-up, the rPAM score was validated as an independent predictor of OS in patients with hematologic disorders undergoing allo-HCT.

Comparison of Risk Scoring Systems in HLA-Matched Related Allogeneic Hematopoietic Stem Cell Transplantation: A Retrospective Cohort Study

Objective

Allogeneic hematopoietic stem cell transplantation (AHSCT) is a potentially curative treatment of choice for many hematological diseases. However, there are some transplantation-related risks. Predicting the risk-benefit ratio prior to AHSCT facilitates the choice of conditioning regimens and posttransplant follow-up. Hence, many risk models have been developed. The aim of the present study was to compare 6 different risk models that are clinically used.

Materials and Methods

A total of 259 patients were enrolled in this study. The European Society for Blood and Marrow Transplantation (EBMT), Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI), Age-Adjusted Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI-Age), revised Pretransplant Assessment of Mortality (rPAM), Acute Leukemia-EBMT (AL-EBMT), and Disease Risk Index (DRI) risk models were applied retrospectively.

Results

The AL-EBMT, HCT-CI, and HCT-CI-Age scoring systems were found to be predictive for 2-year overall survival (OS) and 2-year non-relapse mortality (NRM) (2-year OS: AL-EBMT, reference vs. score 8.5-10, HR: 1.3, p=0.035; AL-EBMT, reference vs. score >10, HR: 3.8, p=0.001; HCT-CI: reference vs. score 1-2, HR: 1.4, p=0.018; HCT-CI: reference vs. score ≥3, HR: 2.5, p<0.001; HCT-CI-Age: reference vs. score 1-2, HR: 1.3, p<0.001; HCT-CI-Age: reference vs. score ≥3, HR: 3.2, p<0.001) (2-year NRM: AL-EBMT: reference vs. score 8.5-10, HR: 1.61, p<0.001; AL-EBMT: reference vs. score >10, HR: 3.3, p<0.001; HCT-CI: reference vs. score 1-2, HR: 1.3, p=0.028; HCT-CI: reference vs. score ≥3, HR: 2.3, p=0.011; HCT-CI-Age: reference vs. score 1-2, HR: 1.3, p=0.01; HCT-CI-Age: reference vs. score ≥3, HR: 2.4, p=0.003). In terms of the Kaplan-Meier estimates of 2-year OS and 2-year NRM, the risk scoring system with the highest predictive power was found to be AL-EBMT (2-year AUC: 0.59 and 0.60, respectively). The other scores were not found to be predictive for 2-year OS and NRM.

Conclusion

In the present study at our bone marrow and stem cell transplant center, it has been demonstrated that the HCT-CI, HCT-CI-Age, and AL-EBMT are good predictors of 2-year NRM and OS.

External validation and comparison of multiple prognostic scores in allogeneic hematopoietic stem cell transplantation

Clinical decisions in allogeneic hematopoietic stem cell transplantation (allo-HSCT) are supported by the use of prognostic scores for outcome prediction. Scores vary in their features and in the composition of development cohorts. We sought to externally validate and compare the performance of 8 commonly applied scoring systems on a cohort of allo-HSCT recipients. Among 528 patients studied, acute myeloid leukemia was the leading transplant indication (44%) and 46% of patients had a matched sibling donor. Most models successfully grouped patients into higher and lower risk strata, supporting their use for risk classification. However, discrimination varied (2-year overall survival area under the receiver operating characteristic curve [AUC]: revised Pretransplantation Assessment of Mortality [rPAM], 0.64; PAM, 0.63; revised Disease Risk Index [rDRI], 0.62; Endothelial Activation and Stress Index [EASIx], 0.60; combined European Society for Blood and Marrow Transplantation [EBMT]/Hematopoietic Cell Transplantation-specific Comorbidity Index [HCT-CI], 0.58; EBMT, 0.58; Comorbidity-Age, 0.58; HCT-CI, 0.55); AUC ranges from 0.5 (random) to 1.0 (perfect prediction). rPAM and PAM, which had the greatest predictive capacity across all outcomes, are comprehensive models including patient, disease, and transplantation information. Interestingly, EASIx, a biomarker-driven model, had comparable performance for nonrelapse mortality (NRM; 2-year AUC, 0.65) but no predictive value for relapse (2-year AUC, 0.53). Overall, allo-HSCT prognostic systems may be useful for risk stratification, but individual prediction remains a challenge, as reflected by the scores' limited discriminative capacity.