Differential Effects of Social Determinants on Cancer Survival by Age at Diagnosis: A Population-Based Study in Alabama

Abstract

Introduction: Social determinants of health (SDOH) are known to influence cancer outcomes. It is unknown whether SDOH effects on cancer survival differ by age at diagnosis or whether known differences in survival by race are consistent across age groups. Since the U.S. population is aging and becoming increasingly racially diverse, it is important to understand how SDOH at both neighborhood and individual levels impact survival in cancer survivors across age groups at diagnosis. Materials and Methods: This retrospective, population-based study utilized data from the Alabama Statewide Cancer Registry of adults (≥18 years) diagnosed with incident breast, prostate, colorectal (CRC), or lung cancers between 2010 and 2019. We included exposures of social vulnerability index (SVI), rural-urban residency, and insurance status at diagnosis. We evaluated an outcome of overall survival (OS) in months from date of diagnosis to date of death or end of follow-up. We estimated Cox proportional hazards regression models stratified by cancer type adjusting for demographics and clinical characteristics. We conducted additional models stratified by age group at diagnosis (≥65 vs. <65 years) and additionally age-race groups. Results: The sample included 26,031 incident breast, 24,567 prostate, 18,821 CRC, and 27,319 lung cancer cases. Across all cancer types, higher SVI was associated with higher risk of death with consistency across age groups. Being insured by Medicare/public insurance was associated with higher risk of death, but effects were higher among those diagnosed <65 and those identifying as White. Discussion: Higher levels of SVI and being insured by Medicare or public insurance are associated with worse survival among adults with breast, prostate, CRC, and lung cancer in Alabama with stronger effects observed among those diagnosed under <65. These results indicate that age at diagnosis is important in contextualizing and understanding differences in survival. Future efforts to improve disparities in mortality among cancer survivors should target interventions to those experiencing social vulnerability and younger at diagnosis. However, given that older adults experience differential care needs, social interventions may improve more proximal drivers of mortality in older adults with cancer such as frailty, but this needs further study.