Why the age group 50-69 years?
Why are only women aged 50-69 invited to BreastScreen Norway?
The public 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).
In 2016, the European Commission Initiative on Breast Cancer (1) carried out a new systematic review of the effect of organised mammography screening. This work has resulted in a strong recommendation that women between the ages of 50 and 69 should be offered mammography screening.
The World Health Organization's (WHO) expert group on breast cancer also published a summary of studies on this topic in 2015 (2). Here, the scientific evidence of mammography screening for the age group 50 to 69 years is confirmed.
What about younger and older women?
There are several factors that contribute to mammography screening not necessarily having the same effect in all age groups. One factor is the incidence of breast cancer. The risk of breast cancer increases with age, and in Norway eight out of ten cases of breast cancer are detected among women over the age of 50.
Another important factor is that mammography in general may be less effective for younger women. Mammographically dense glandular tissue is more common in younger than older women. Dense glandular tissue appears grey on mammograms and this can mask cancerous tumours. In comparison, older women's breasts more often contain more fatty tissue, which appears as a darker grey on mammograms and thus provide better contrast to the greyish-white colour that breast cancer tumours often have.
This can often make it more difficult to detect breast cancer on mammograms from younger women, compared to older women. A higher number of younger women must therefore undergo additional examinations to detect breast cancer. This naturally also means that several young women who do not have breast cancer, have to be called back for additional examinations. This is regarded as a disadvantage, and must be weighed against the potential benefit of more life years gained among younger women.
Recent documentation from expert groups in the EU and WHO shows that organised screening can also reduce breast cancer mortality for women aged 45 to 49 years and 70 to 74 years (1, 2).
The EU expert group makes a conditional recommendation on 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 background for these assessments is described in detail here.
In 2015, the WHO expert group concluded that there is sufficient evidence that organised screening reduces breast cancer mortality for women aged 70 to 74, while they believe that the effect for women in the age group 40 to 49 years is not sufficiently documented for them to be able to recommend organised screening (2).
Since the WHO's conclusion came earlier than that of the EU group, some studies were not included in the WHO's review. This is part of the reason why the two expert groups have reached different conclusions for women younger than 50 years.
In the hands of the Ministry of Health and Care Services
The Cancer Registry of Norway believes that an expansion of the age groups in mammography screening should be discussed and reassessed by Norwegian health authorities on the basis of the updated results and recommendations from the EU and WHO.
In 2019, the Norwegian Association for Radiological Breast Diagnostics asked the health authorities to consider expanding the age groups in BreastScreen Norway. The case is under consideration in the Directorate of Health.
It is the Ministry of Health and Care Services that must make the decision to expand the program, but before such a decision can be made, the Cancer Registry of Norway believes that the issue should be investigated according to Norwegian conditions.
In Europe, where organised mammography screening is recommended by most health authorities, it varies which age groups are invited to screening. Most countries target 50-69 year olds, but countries such as England, the Netherlands and Sweden include women who are both younger and older than 50 and 69 years.
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.