Social Vulnerability Is a Clinically Important Predictor of Outcomes after Allogeneic Hematopoietic Cell Transplantation

Introduction: Allogeneic hematopoietic cell transplantation (HCT) is an established treatment for malignant and non-malignant hematologic diseases. However, HCT is not without risk; rates of non-relapse mortality (NRM) remain high during the first year after transplantation. Clinical prediction models have been developed to identify those at increased risk for NRM after HCT, but the impact of social determinants of health on transplant outcomes has not been well characterized. To address this gap, we evaluated the relationship between census tract-level social vulnerability and 1y NRM following HCT. Methods: Using a retrospective cohort design, this study included 1,602 patients living in California (CA) who underwent a first allogeneic HCT between 2013-2019 at City of Hope. Demographic, insurance, disease, treatment, and survival information was abstracted from the medical records. Social vulnerability according to the census tract was measured using the Social Vulnerability Index (SVI), a tool developed by the Center for Disease Control. SVI comprises 4 themes (socioeconomic status [SES], household composition & disability, minority status & language, and housing & transportation) constructed using 15 social and environmental variables from the US Census. This study used the overall SVI and individual theme scores which were ranked across the CA census tracts as percentiles; the scores ranged from 0 (least vulnerable) to 100 (most vulnerable). Scores were assigned to patients using their address at the time of HCT. Fine-Gray multivariable regression was used to evaluate the association between SVI, tertiles of SVI, and 1y NRM, adjusted for age at HCT, performance status, relapse risk (RR), human leukocyte antigen (HLA) match, and HCT-Comorbidity Index (HCT-CI). We also performed subgroup analysis to examine the risk of NRM across combined SVI and HCT-CI categories: 1) lower two SVI tertiles (low social vulnerability) and low (