Conditional survival disparities and determinants in Urban-Rural patients with papillary thyroid carcinoma.

BACKGROUND

Urban-rural disparities are significant determinants of cancer outcomes; however, population-based long-term dynamic survival differences in papillary thyroid carcinoma (PTC) remain unclear. Utilizing the US Surveillance, Epidemiology, and End Results (SEER) database, this study aimed to unveil the spatiotemporal evolution of urban-rural disparities in PTC through conditional survival analysis for the first time, and to identify modifiable influencing factors, thereby providing evidence for precision public health strategies.

METHODS

We conducted a retrospective cohort study based on the US SEER-18 database (2000–2019), with urban-rural classification defined according to the Office of Management and Budget standards. Survival disparities were assessed using the Kaplan-Meier method, and multivariate adjustments were performed using Cox proportional hazards models. Conditional survival analysis (CS(y|x) = S(x + y)/S(x)) was applied to quantify the dynamic evolution of survival probabilities. Stratified analyses based on metastatic status and surgical intervention were performed to elucidate the sources of heterogeneity in these disparities.

RESULTS

This study analyzed 170,505 PTC patients. Multivariable analysis confirmed age ≥ 55, male sex, advanced tumor stage, and non-married status as independent risk factors for disease-specific death, with surgery being a strong protective factor. Notably, advanced tumor stage, especially distant metastasis, posed a greater mortality risk for rural patients. Survival analysis demonstrated a superior long-term prognosis for urban patients, with a 20-year disease-specific survival rate of 97.5% versus 97.1% for rural patients. The survival gap widened over time. Death hazard rates were higher in rural patients within the first decade after diagnosis, exhibiting a distinct dynamic pattern. While conditional survival improved with longer elapsed time in both groups, urban patients established a sustained advantage after 6 years post-diagnosis.Stratified analyses revealed that the urban–rural survival disparity was most pronounced among males, patients with distant metastasis, and those not undergoing surgery. Importantly, undergoing surgery significantly narrowed this prognostic gap.

CONCLUSION

This study employs conditional survival analysis to reveal that urban-rural survival disparities in PTC patients exhibit dynamic time-varying characteristics. The core mechanism lies in the inequality of healthcare resource accessibility, which leads to gaps in the long-term management of high-risk patients. This provides critical evidence for implementing targeted regional intervention strategies.