Cancer
Impact of Regional Factors on Breast Cancer Stage at diagnosis: Exploring Age-Specific Differences Around Korea’s National Cancer Screening Policy Eunhye Park* Eunhye Park
Background: Breast cancer incidence is rising in South Korea, with widening regional disparities in outcomes. The national breast cancer screening program targets women aged 40 and over. However, the influence of regional factors, such as the Area Deprivation Index (ADI), on breast cancer stage at diagnosis remain underexplored, particularly with limited studies considering screening age.
Objective: To examine the impact of regional factors, including ADI and other risk factors, on breast cancer stage at diagnosis in women under and over 40 years of age.
Methods: The Korea National Cancer Incidence Database (2014–2018) were analyzed at 250 administrative municipal levels. Breast cancer stages were classified using SEER summary stages. Bayesian hierarchical models evaluated associations between breast cancer incidence and regional factors.
Results: Among 105,755 breast cancer cases, 10,748 were aged 20–39 years, and 95,007 were aged 40 and older. Overall, lower ADI (β = -0.033, 95% Credible Interval [CrI] = -0.052, -0.014), lower obesity rates, higher alcohol consumption, and greater mammography availability were associated with higher breast cancer incidence. Localized breast cancer negatively associated with ADI overall, while distant-stage cancer showed a positive association. In women aged 40 and older, localized breast cancer was negatively associated with ADI (β = -0.046, 95% CrI = -0.073, -0.019), reflecting early detection benefits. Conversely, women aged 20–39, localized breast cancer was positively associated with ADI (β = 0.059, 95% CrI = 0.008, 0.111), suggesting that breast cancer risk factors are more prevalent in deprived areas within this age group.
Conclusions: ADI has opposing effects on breast cancer incidence by summary stage. Efforts to reduce regional disparities in breast cancer incidence should focus on age-specific regional risk factors and improving early detection.
