Urban-Rural Disparities in Treatment and Outcomes for Colorectal Liver Metastases in the United States: A SEER-Medicare Analysis.

BACKGROUND: Curative-intent resection of colorectal liver metastases (CRLM) offers an opportunity for long-term survival, yet access barriers correlated with area-level socioeconomic status (SES) and rurality may drive disparities in cancer care. Prior work shows lower liver-directed therapy use and survival in socioeconomically disadvantaged conditions, whereas the association between rurality and CRLM treatment and prognosis has not been previously studied. METHODS: We conducted a retrospective population-based cohort study using the Surveillance, Epidemiology, and End Result-Medicare database (2000-2020) among patients aged 66-85 years with isolated CRLM. Urban-rural status was determined by using USDA Rural-Urban Commuting Area codes. Associations between rurality, receipt of therapy, and overall survival were evaluated by using multivariable logistic regression and Cox proportional hazards models, adjusting for patient and tumor characteristics. RESULTS: Among 34,781 patients with isolated CRLM, 21.7% resided in rural areas. Rural patients were more likely to have rectal primary tumors (adjusted odds ratio [aOR] [95% confidence interval (CI)] 1.13 [1.04-1.24], p = 0.01) and synchronous metastatic disease (aOR [95% CI] 1.09 [1.02-1.17], p = 0.01). Rural residence was associated with higher odds of primary tumor resection (aOR [95% CI] 1.12 [1.02-1.22], p = 0.01), but lower odds of systemic chemotherapy (aOR [95% CI] 0.86 [0.81-0.92], p < 0.01) and curative-intent liver directed therapy (aOR [95% CI] 0.89 [0.80-0.99], p = 0.03). Rural residence was independently associated with worse overall survival (hazard ratio [HR] (95% CI) 1.08 [1.05-1.12], p < 0.01). CONCLUSIONS: Rural patients with CRLM were less likely to receive liver directed therapy and experienced inferior survival. These findings highlight persistent geographic disparities in cancer care delivery and outcomes.