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.