Why the age group 50-69 years?

Norwegian health authorities recommend mammography screening for women aged 50-69 years. This is in line with European guidelines and recommendations from the World Health Organization.

Last updated: 12/3/2024

The breast cancer screening program in Norway, BreastScreen Norway, offers mammography screening to women aged 50 to 69 years. The age group has remained the same since the program started in 1995, and was chosen after extensive discussions in professional groups about whether younger and/or older women also should be included.

The age group 50 to 69 years was chosen because the scientific evidence showing that organised mammography screening reduces breast cancer mortality was strongest for this age group. This is still the case (1, 2).

More recently (2016 and 2015, respectively), both the EU and the World Health Organization (WHO) expert groups on breast cancer have published updated reviews confirming the effect and strengthening the recommendations for mammography screening for the age group 50 to 69 years.

What about younger and older women?

The recent reviews from the expert groups in the EU and WHO have also shown that organized screening can reduce breast cancer mortality for women aged 45 to 49 years and 70 to 74 years (1, 2).

The EU expert group has given a conditional recommendation for mammography screening for the age groups 45 to 49 years and 70 to 74 years, but does not recommend screening for women aged 40 to 44 years.

The WHO expert group concludes that organized screening reduces breast cancer mortality for women aged 70 to 74 years, but that the effect for women aged 40 to 49 years is not sufficiently documented to recommend organized screening (2). The reason that the two groups came to different conclusions for women younger than 50 years is, among other things, that some studies were not included in the WHO review as it was conducted at an earlier time when results from studies of women aged 45-49 years were not available.

Different effects in different age groups

Mammography screening does not have the same effect in all age groups. There are several reasons for this. One factor is the incidence of breast cancer. The risk of breast cancer increases with age, and in Norway, eight out of ten breast cancer cases are detected among women over 50 years of age.

Another important factor is that mammography may be less effective for younger women. This is because dense glandular tissue is more common in younger women than in older women. Such dense tissue appears almost white on mammograms, which is very similar to the color breast cancer tumors appear with. This means the dense tissue can hide breast cancer. Older women often have more fatty tissue in their breasts, which appears darker gray on mammograms and thus provides a better contrast to the light color breast cancer tumors often have.

This means it may be more difficult to detect breast cancer on mammograms taken of younger women, compared to older women. More of the younger women therefore also need to undergo additional examinations. This also means that more of the younger women who do not have breast cancer have to be called back for additional examinations - so-called "false alarms". This is considered a disadvantage, and must be weighed against the potential benefit of more life years gained among the younger women.

Ongoing assessment by the Norwegian Directorate of Health

Based on the updated reviews and recommendations from the EU and WHO, the Cancer Registry of Norway considers the evidence of effects sufficient for the Norwegian health auhorities to make an assessment of expanding age groups.

The Norwegian Directorate of Health has initiated such an assessment, on the basis of a proposal in 2019 from the Norwegian Association for Radiological Breast Diagnostics.

It is the Ministry of Health and Care Services that makes decision about whether the program should be expanded. In Europe, where most health authorities now recommend organized mammography screening, the age groups invited vary. Most countries include the 50-69 age group, while countries such as England, the Netherlands and Sweden include women younger and/or older than 50 and 69 years.

References:

European Commission Initiative on Breast Cancer. Breast cancer guidelines and quality assurance.

World Health Organization. Breast-Cancer Screening - Viewpoint of the IARC Working Group. IARC Press 2015.

Why the age group 50-69 years?

What about younger and older women?

Different effects in different age groups

Ongoing assessment by the Norwegian Directorate of Health

References:

Other articles and pooled studies on mammographic screening:

Cancer Registry of Norway