Limitations of Applying the Hematopoietic Cell Transplantation Comorbidity Index in Pediatric Patients Receiving Allogeneic Hematopoietic Cell Transplantation.

Abstract Identifying which patients are at high risk for transplant related mortality, prior to allogeneic hematopoietic cell transplantation (alloHCT) is crucial both to guide decision-making with patients and families and to inform the alloHCT approach. There is a paucity of data evaluating the utility of the HCT comorbidity index (HCT-CI) in pediatric patients. We performed a retrospective cohort study of 188 patients who underwent alloHCT between January 2008 and October 2016 and assessed pre-transplant comorbidities defined and weighted by the HCT-CI. The primary endpoint of our study was overall survival (OS). Kaplan-Meier method was used to assess survival estimates at one-year post-transplant and did not differ based on HCT-CI scores: 78.7% (SE 6.69%) for HCT-CI=0, 74.7% (SE 6.33%) for HCT-CI=1-2, 77.3% (SE 4.17%) for HCT-CI ≥3. Multivariable Cox proportional hazards analysis did not show HCT-CI having an effect on OS: hazard ratio (HR) 0.633 (95% Confidence Interval [CI] 0.297-1.347) for HCT-CI scores 1-2, HR 0.935, (95%CI CI 0.456-1.918) for HCT-CI scores ≥3, compared to scores of 0. The most frequent comorbidities observed were hepatic disease (mild in 29%, severe in 23%) and pulmonary disease (moderate in 15% and severe in 29%). However, only 55% were able to complete pulmonary function testing (PFT). Hepatic disease was based on transaminitis in 48% and by bilirubin alone in 26% of patients; 46% of patients with hepatic dysfunction had an underlying hemoglobinopathy and hyperbilirubinemia related to ongoing hemolysis. This study evaluates HCT-CI comorbidities in greater detail than has been performed previously in children undergoing alloHCT. We identify challenges with the HCT-CI in the pediatric population and highlight the comorbidities that may benefit from adjustments to their definition to create an improved risk assessment tool for children.