Benefits and harms

Norwegian health authorities recommend breast cancer screening every other year for all women between the ages of 50 and 69 (1). This is in line with recommendations from the World Health Organization (2) and the EU (3). The benefit of breast cancer screening is best documented in the 50 to 69 age group.

Routine examinations such as breast cancer screening has both advantages and disadvantages.

If you have received an invitation to attend BreastScreen Norway, you can read about this below to decide whether you will accept the offer.

The figure below illustrates the expected results when 1000 women attend BreastScreen Norway (click on the figure for a larger image).

Benefits of breast cancer screening 

Fewer deaths from breast cancer: The most important benefit
of breast cancer screening is fewer deaths from the disease.
This has been shown in a number of studies (4). A conservative
estimate of the effect is shown in the figure below. 

More gentle treatment: Screening allows breast cancer to be detected at an earlier stage. This increases the possibility of keeping your breast after an operation, and for more gentle treatment (5).

Disadvantages of breast cancer screening

False alarm: If the mammograms show changes in your breast, you will be called back for additional tests. For most women, these tests show that the changes are harmless, and that it was a “false alarm” (6).

Stress and anxiety: Some may feel anxiety and stress while waiting for their results and if they are called back for additional tests (7).

Overdiagnosis og overtreatment: We find more breast cancer among women who go to screening than among those who do not go to screening. One reason is that some breast cancer tumours grow so slowly that they would not have been detected if the women had not been screened.

It is possible to tell the difference between breast cancers that have the ability to grow slowly and those that have the ability to grow quickly, and adjust the treatment accordingly. However, it is impossible to tell which breast cancers grow so slowly that it is not necessary to provide treatment. This means that some women receive too much treatment. We do not know which women this applies to, but we know that they are mainly in the group that receives the gentlest treatment.

Since we can’t tell which breast cancers do not need treatment, we can’t count them either. Based on our current knowledge, our best estimate of the extent of overdiagnosis is illustrated in the figure at the top of this page, which shows that when 6 breast cancer tumours are detected among 1000 attending women, 1 of them is assumed to be overdiagnosed/overtreated (7). 

If breast cancer is detected

If breast cancer is detected, you will receive follow-up at the breast centre. Screening, diagnostics and treatment are based on national guidelines and interdisciplinary collaboration (1).

You can find information about breast cancer on websites from the Cancer Society or (in Norwegian) helsenorge.no.

Mammograms do not find all breast cancers

Mammograms do not find all breast cancers. Breast cancer can also be discovered between two screenings (6).

For this reason, you should always consult a doctor if you notice a new lump or changes in your breast, even if you recently had a mammogram.

X-rays

Mammography uses X-rays, which in theory can increase the risk of developing breast cancer.

The risk is very low, even with regular participation in BreastScreen Norway (8).

More information

The data sources and methods used for calculating effects of breast cancer screening, are complex. We have simplified the information presented on this page, but more detailed information is available here. 

You can also talk to your doctor about breast cancer screening.

References

1. Brystkreft handlingsprogram. Nasjonal faglig retningslinje. (National guidelines for diagnosis, treatment and follow-up of patients with breast cancer). In Norwegian. Published by the Norwegian Directorate for Health Services. 

2. International Agency for Research on Cancer (2016) Breast Cancer Screening. IARC Handbook of Cancer Prevention, vol 15. IARC Handbook of Cancer Prevention Lyon, France.

3. Breast cancer guidelines and quality assurance. European Commision Initiative on Breast Cancer. 

4. Worldwide Review and Meta-Analysis of Cohort Studies Measuring the Effect of Mammography Screening Programmes on Incidence-Based Breast Cancer Mortality. Dibden A. et al. Cancers. 2020;12(4).

5. Kirurgisk behandling av brystkreft i Norge 2003-18. Skjerven HK et al. Tidsskriftet den norske legeforening, published 26.10.20

6 The Norwegian Breast Cancer Screening Program, 1996-2016: celebrating 20 years of organised screening in Norway Cancer in Norway 2016 - cancer incidence, mortality, survival and prevalence in Norway. Published 2017 by the Cancer Registry of Norway. 

7. Research-based evaluation of the Norwegian Breast Cancer Screening Program. Final report. Published 2015 by the Research Council of Norway.

8. The risk of radiation-induced breast cancers due to biennial mammographic screening in women aged 50-69 years is minimal. Hauge IH et al. Acta Radiologica, 2013.