Impact of small area-level deprivation on survival outcomes in patients with Cholangiocarcinoma: a population-based multilevel survival analysis

Background Cholangiocarcinoma (CCA) carries a dismal prognosis. Beyond clinical determinants, socioeconomic deprivation may also influence outcomes. Busan, a rapidly aging metropolitan area in Korea, provides a critical setting for evaluating how area-level deprivation interacts with individual risk factors for CCA survival. However, evidence regarding the effect of area-level deprivation on CCA survival remains scarce, particularly within the Korean population. We aimed to evaluate the association between the deprivation index (DI) and individual clinical factors and provide a deeper understanding of the variability in the survival rates of patients with CCA in Busan. Methods We analyzed data from 12,950 patients diagnosed with CCA between 2003 and 2020 using the Busan Regional Cancer Registry linked with national death records. Individual-level variables included age, sex, stage, and year of diagnosis, while area-level deprivation was quantified using the census-derived DI. Multilevel survival analyses were performed using a frailty Cox proportional hazards model with a random intercept for region to estimate hazard ratios (HRs) for both individual- and regional-level predictors. Results The median survival period was 42 weeks. Survival declined with age (46.5% vs. 21.3% in patients aged 0–44 years and ≥75 years, respectively, p < 0.001) and was significantly lower in advanced-stage disease (47.7% localized vs. 8.07% distant, p < 0.001). Men had marginally higher survival rates than women (33.8% vs. 32.1%, p < 0.001). Deprivation strongly influenced prognosis, as patients in the most deprived areas had a 30.1% survival rate compared with 36.3% in the least deprived areas (p < 0.001). In fully adjusted models, age ≥75 years (HR 2.68), regional (HR 1.40) and distant stages (HR 3.77), and higher DI (HR 1.06 per unit) independently predicted poorer survival. Incorporating DI into the models slightly reduced the between-region variance ( σ ) and median hazard ratio (MHR), indicating that area-level deprivation partially explains regional differences in survival outcomes. Conclusion CCA survival in Busan is influenced by both individual vulnerability and area-level deprivation. Older age, advanced stage, and higher deprivation were identified as independent poor prognostic factors for CCA survival. In super-aged urban societies, integrating social determinants into clinical care is essential to reduce inequities and improve outcomes.