Breast cancer in Switzerland: a comparison between organized-screening versus opportunistic-screening cantons

Switzerland is one of the few remaining European countries without a uniform national breast cancer screening program. Most Swiss cantons have initiated mammography screening programs, with the notable exceptions of the cantons of central Switzerland. The aim of this study is to compare the TNM (tumor-node-metastasis) status in woman diagnosed with screen- and non-screen-detected breast cancers. We compare TNM of breast cancers of cantonal screening cantons (Or-SC) with organized mammographic screening and opportunistic-screening cantons (Op-SC) without organized mammographic screening.

We compared the TNM documented in cantons with organized screening (Or-SC) in the national cancer registry with those in the cantons of central Switzerland without organized screening (Op-SC) between 2014 and 2020. Since 2014, a total of 19 236 patients from Or-SC and 2282 from Op-SC with breast cancer were compared. Age groups were defined as younger than 50 years, between 50 and 69 years, and older than 70 years.

By comparison, women aged 50-69 years in the cantons of the Op-SC group exhibited significantly larger tumors T1-3 [point estimate of the difference with 95% confidence interval (CI) for T1: -7.7% (95% CI -11.0% to -4.4%); T2: 5.3% (95% CI 2.2% to 8.5%); T3: 2.5% (95% CI 0.8% to 4.2%)] and significantly fewer proportion of N0 [-5.7% (95% CI -9.0% to -2.5%)] without significant difference in the M status (P = 0.97).

Our study shows that patients aged 50-69 years from Op-SC have significantly larger tumors and higher incidence of lymph node metastases than women in the corresponding Or-SC group. This globally unique case within one single small country with very high living standards, but with different screening strategies, indicates the benefits of organized breast screening programs.