Organized breast cancer screening programs provide national access to two-view digital mammography, followed by diagnostic assessment for abnormal findings. Screening ages and intervals for breast cancer may vary internationally. In the United States, annual screening is generally recommended, whereas Denmark typically implements biennial screening and the United Kingdom triennial screening. Nationwide biennial breast cancer screening for women aged 50-69 years was fully implemented by 2009 across Denmark. It is well managed through five regions, with free cancer treatment available. This program’s performance is monitored using outcome and process indicators such as rates of advanced-stage incidence. Because the stage at diagnosis strongly identifies mortality, a recent study published in the Journal of the National Cancer Institute evaluated the stage-specific survival using screening history to determine whether improved survival reflects earlier diagnosis and to better estimate future breast cancer mortality.
In this nationwide register-based cohort study, a total of 817,128 women with no history of breast cancer were invited to participate in the Danish breast screening program from 2010 to 2019 with follow-up through November 2022. These participants had turned 50 years of age before the end of 2014. All participants were followed until emigration, study end, or death. Data related to survival, screening, staging, cancer, demographics, and treatment were obtained through linking 5 national registries, like the Pathology register, Danish quality database for mammography screening (DKMS), civil registration system, national patient register, and cancer registry. The stage was prioritized due to the availability of unreliable pathology data. Treatments received within one year of breast cancer diagnosis were categorized as no treatment, non-surgical therapy, or surgical therapy. Statistical analyses focused on stage-specific survival for invasive cancers (stages I-IV and unknown).
Among 817,128 eligible women, 32,827 were diagnosed with breast cancer. Of these, 82% (n = 27,007) were diagnosed before age 70 years, and 5820 after 70 years. Overall, 9% (n = 2,991) of cancers were stage 0, 46% (n = 14,985) were stage I, 31% (n = 10,312) were stage II, and 8% (n = 2,787) were stage III-IV. Screen-detected cancers were more frequently in early stage (0-I), and less often stage III-IV, compared to non-screen-detected cancers.
Among women younger than 70 years, 5-year net survival for stage I was 99.6% (95% confidence interval [CI]: 99.2%-100%) in screen-detected, 97.1% (96.2%-98.1%) in symptomatic ever-screened, and 97.6% (96.1%-99.1%) in never-screened women. For stage II, survival was 96.7% (95.9%-97.5%), 93.3% (92.1%-94.5%), 93% (91.4%-94.7%), respectively. Stage III survival reached 90.5% (87.6%-93.5%) in screen-detected, 76.3% (72.3%-80.7%) in never-screened cases, and 80.7% (77.2%-84.4%) in symptomatic ever-screened cases. The largest difference occurred in stage IV, in which 5-year survival was found to be 74.7% (65.5%-85.1%) in screen-detected vs 32.4% (27%-38.8%) in never-screened women, and 10-year survival was found to be 61.5% (50.2%-75.3%) vs 17.1% (12.4%-23.5%).
Among 547 stage IV cases before age 70 years, 67% of screen-detected women received surgery, whereas 23% of never-screened women did not. Furthermore, median survival was 6 years (3.4-10) with surgery, 2 years (0.8-4) with non-surgical treatment, and one year (0-0.3) with no treatment.
This study’s limitations include defining screening implementation as January 1, 2010, causing minor classification, its observational design, use of net survival, limited treatment data, missing sociodemographic factors, and limited generalizability.
In conclusion, this study highlights that screen-detected breast cancers show no worse stage-specific survival compared to nonscreen-detected cases. Survival estimates are reliable for stages I–III, with minimal screening bias. However, stage IV screen-detected cancers demonstrate better survival. Reductions in stage II–IV incidence through screening likely translate into lower breast cancer mortality with longer follow-up.
Reference: Tickle A, Offman J, North B, Jørgensen SF, Njor S, Sasieni P. Improved stage-specific survival in screen-detected breast cancer in Denmark: a cohort study. JNCI 2026;djaf377. doi:10.1093/jnci/djaf377
