Spatial Disparities in Stage-Specific Breast Cancer Incidence and Area-Level Risk Factors in Korea, 2005-2018

Despite a nationwide breast cancer screening program in Korea, spatial disparities in stage at diagnosis persist. This study aimed to examine disparities in breast cancer incidence by stage and their association with area-level risk factors.

We conducted a population-based ecological study using data from the Korea National Cancer Incidence Database (2005-2018). Among 230,214 women diagnosed with breast cancer, 215,803 with known stage were included. Stage-specific incidence across 250 municipalities was estimated for three periods (2005-2008, 2009-2013, and 2014-2018). For 2014-2018, associations with the area deprivation index (ADI), obesity rate, alcohol consumption rate, cancer screening rate, and mammography unit availability were assessed using Bayesian hierarchical models.

Of 215,803 patients, 59.0% had localized-stage, 35.5% regional-stage, and 5.5% distant-stage. Localized-stage incidence was higher in affluent areas, whereas distant-stage incidence was higher in deprived areas. In multivariable models, lower ADI (β = -0.058; 95% credible interval [CrI]: -0.098, -0.019), lower obesity rate (β=-0.066; 95% CrI: -0.091, -0.041), and higher mammography availability (β=0.014; 95% CrI: 0.001, 0.027) were significantly associated with higher localized-stage incidence. Conversely, higher ADI (β=0.103; 95% CrI: 0.017, 0.188) and higher alcohol consumption (β=0.227; 95% CrI: 0.115, 0.338) were significantly associated with increased distant-stage incidence.

Spatial disparities in stage-specific breast cancer incidence in Korea were associated with area-level deprivation, healthcare resources, and health-related behaviors. Integrating spatial perspectives into cancer control strategies may help promote more equitable early detection and contribute to improve breast cancer outcomes.