Breast cancer mortality in participants of the Norwegian Breast Cancer Screening Program

Cancer. 2013 Sep 1;119(17):3106-12. doi: 10.1002/cncr.28174. Epub 2013 May 29.


Background: The Norwegian Breast Cancer Screening Program started in 1996. To the authors' knowledge, this is the first report using individual-based data on invitation and participation to analyze breast cancer mortality among screened and nonscreened women in the program.

Methods: Information on dates of invitation, attendance, breast cancer diagnosis, emigration, death, and cause of death was linked by using unique 11-digit personal identification numbers assigned all inhabitants of Norway at birth or immigration. In total, 699,628 women ages 50 to 69 years without prior a diagnosis of breast cancer were invited to the program from 1996 to 2009 and were followed for breast cancer through 2009 and death through 2010. Incidence-based breast cancer mortality rate ratios (MRRs) were compared between the screened and nonscreened cohorts using a Poisson regression model. The MRRs were adjusted for calendar period, attained age, years since inclusion in the cohorts, and self-selection bias.

Results: The crude breast cancer mortality rate was 20.7 per 100,000 women-years for the screened cohort compared with 39.7 per 100,000 women-years for the nonscreened cohort, resulting in an MRR of 0.52 (95% confidence interval, 0.47-0.59). The mortality reduction associated with attendance in the program was 43% (MRR, 0.57; 95% confidence interval, 0.51-0.64) after adjusting for calendar period, attained age, years after inclusion in the cohort, and self-selection bias.

Conclusions: After 15 years of follow-up, a 43% reduction in mortality was observed among women who attended the national mammographic screening program in Norway.

Keywords: Norway/epidemiology; breast neoplasms/mortality; breast neoplasms/prevention and control; breast neoplasms/radiography; female; mammography; mass screening.

Publication types

  • Comparative Study

MeSH terms

  • Aged
  • Breast Neoplasms / diagnostic imaging*
  • Breast Neoplasms / epidemiology
  • Breast Neoplasms / mortality*
  • Breast Neoplasms / prevention & control
  • Cohort Studies
  • Early Detection of Cancer*
  • Female
  • Follow-Up Studies
  • Humans
  • Incidence
  • Mammography*
  • Mass Screening*
  • Middle Aged
  • Norway / epidemiology
  • Registries
  • Selection Bias
  • Survival Rate