Utility and Validity of Hematopoietic Cell Transplantation-Comorbidity Index (HCT-CI) in Predicting Overall Survival and Non-Relapse Mortality in Adolescent and Young Adult Population

Introduction: Hematopoietic cell transplantation-comorbidity index (HCT-CI) is a scoring tool of pretransplant comorbidities that is widely used to predict posttransplant overall survival (OS) and non-relapse mortality (NRM). It was initially studied and validated on cohorts of patients from two institutions with higher HCT-CI score predicting higher NRM and lower OS. Median age of patients in those cohorts was 44.8 (0.8-72.2). Further studies from multiple centers showed similar results however, most of these studies included patients older than 40 years. One study looked at the usefulness of HCT-CI in adolescent and young adult (AYA) population and found that HCT-CI might be useful in predicting OS but not NRM, although the sample size was only 56 patients.

We aim in this study to test the utility and validity of HCT-CI for predicting OS and NRM in a larger cohort of AYA patients undergoing allogenic stem cell transplant in our center.

Methods: We conducted a retrospective cohort, single center study. Only patients between the ages of 14 and 40 years were included. Patients were divided into 3 groups according to HCT-CI: 0, 1-2, or more than 2. Causes of death were assigned as either relapse related versus non-relapse related mortality. Patients have to be seen in clinic at least once after discharge to be included.

Results: 499 patients were included in the study. Median age was 24 years. 292 (58.5%) male and 207 (41.5%) female (P = 0.4). Among those patients, 184, 162 and 153 were having HCT-CI of 0, 1-2 and more than 2 respectively (P = 0.4). 361 (73%) patients were having malignant disease while 138 (27%) were having non-malignant disease (P = 0.18). 2-year and 4-year NRM were 8.6% and 16.1% for HCT-CI 0, 9.8% and 20.4% for HCT-CI 1-2, 10% and 16.18 for HCT-CI more than 2 (P = 0.9). 2-year and 4-year OS were 75.7% and 62% for HCT-CI 0, 69.7% and 58.5% for HCT-CI 1-2, 63.5% and 53.7 for HCT-CI more than 2 (P = 0.06). There was no statistically significant difference among all 3 groups in terms of OS or NRM.

Conclusion: HCI-CI was not predictive of neither OS nor NRM in our cohort of patients aged between 14 and 40 years. Limitations of our study include the retrospective nature of data collection as well as being a single center-based study. Larger prospective studies in this particular age group would help to more accurately risk stratify patients and predict their post-transplant course.

No relevant conflicts of interest to declare.