A study looking at differences in breast density between different ethnic groups

Cancer type:

Breast cancer





This study looked at how breast tissue looks on the mammograms of women from different ethnic groups.

The breasts are made up of dense glandular tissue. Once a woman is past her menopause Open a glossary item, the glandular tissue is gradually replaced by fat, which is less dense. Doctors use the term ‘breast density’ to describe how breasts look on a mammogram.

Women from the Caribbean, West Africa and India have a much lower risk of breast cancer than women from the UK. When women from these low risk countries come to live in the UK, they and their children still have a lower risk of breast cancer than white British women.

In this study, researchers wanted to find out if there were differences in breast density between women from 3 ethnic groups. The aim of the study was to see if differences in breast density could help to explain why there was a difference in breast cancer risk between the groups.

Summary of results

The researchers found that breast density was lowest in South Asian women and highest in white women.

The study included 645 women who were between 50 and 64 years old. It was carried out at a breast screening service in London.

The researchers gathered information about the women’s breast cancer risk factors from questionnaires and telephone interviews. They found that both South Asian and Afro-Caribbean women had more factors that help to protect against breast cancer including

  • Starting their periods later
  • Being shorter in height
  • Having more children
  • Having their first child at an earlier age
  • Being less likely to use HRT
  • Being more likely to breast feed their children

These factors can all offer some protection against breast cancer, but not enough to completely explain the lower rates of breast cancer in these 2 groups.

By studying the women’s mammograms, the researchers could see that both Afro-Caribbean women and South Asian women also had less dense breasts.

They suggest that the protective factors listed above can account for some of the difference in density, but not all of it. Other factors, such as diet and genetics may also have an effect. The researchers suggest that this should be studied more.

We have based this summary on information from the team who ran the study. The information they sent us has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. The figures we quote above were provided by the study team. We have not analysed the data ourselves.

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How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Ms Valerie McCormack

Supported by

Cancer Research UK

Freephone 0808 800 4040

Last review date

CRUK internal database number:

Oracle - 580

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Deborah wanted to help other breast cancer patients in the future

A picture of Deborah

“Deborah agreed to take part in a trial as she was keen to help other cancer patients in the future. "If taking part in a trial means others might be helped then I’m very happy with that."

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