Imagine a 57-year-old woman, let’s call her Maria, who’s just opened a letter about her mammography results. She’s had several mammograms before, but this time reads new information: “Your breasts are dense”.

While the letter assures her that dense breasts are common, it also indicates it could make it harder to see breast cancer on the mammogram.

Maria is confused about what to do next and wonders if she should be worried. Does she need to see her GP?

Maria may be fictional but she reflects the findings from the first trial of its kind we publish today.

We show women notified they have dense breasts alongside their mammogram result are more confused and anxious, do not feel more informed, and have greater intentions to see their GP for advice.

Remind me, what is breast density?

Dense breast tissue appears white on a mammogram and can hide (or mask) a cancer, which also appears white.

Dense breasts are very common. About 25–40% of women are considered to have dense breasts.

Breast density is one of several independent risk factors for breast cancer. After years of consumer advocacy, more women are being told about their breast density when they get their results from breast cancer screening.

The idea is simple: let women know if they have dense breasts – something that can raise cancer risk and make mammograms harder to read – so they can decide whether to get extra testing, such as an ultrasound or MRI.

Notifying women about their breast density is now legislated in the United States, recommended in Australia, and is being considered in other jurisdictions, such as the United Kingdom.

This is despite the lack of robust evidence on whether the benefits of notifying breast density at screening outweigh potential harms for women, and the impact on health services.

What we did and what we found

Our trial was co-designed with BreastScreen Queensland. From September 2023 to July 2024 we randomised 2,401 women (average age 57) who had a clear mammogram (their mammogram didn’t show cancer), but had dense breasts, into three categories:

1. Control: no notification of dense breasts (standard care)
2. Intervention 1: notification of breast density as part of the screening results letter plus extra written information in a leaflet
3. Intervention 2: notification of breast density as part of the screening results letter plus a link to extra information in an online video.

Eight weeks after screening, we found women notified they had dense breasts felt more anxious and confused about what to do about their breast health compared to the control group.

They also did not feel more informed to make decisions about their breast health, and had greater intentions to discuss this with their GP.

We haven’t followed participants for long enough yet, nor was the trial specifically designed to see if notifying women about their breast density led to extra cancers being detected.

The trial also had some limitations. For example there was a low proportion of women from non-English speaking backgrounds.

However, this is the first randomised trial world-wide to evaluate the immediate impact of breast density notification on women in the context of mammography screening.

It provides evidence for breast screening programs internationally to carefully consider the potential impact of such notification.

What next?

In Australia, where breast density notification is now recommended, it is important we acknowledge that the topic of breast density may be confusing and some women may be worried.

Communicating about breast density, including public messaging, should be focused on density being one of many risk factors for breast cancer and that there are other potentially modifiable ways to reduce a woman’s overall risk.

This includes maintaining a healthy weight, being physically active, reducing alcohol intake, and not smoking. Messaging should also emphasise that mammograms remain the best way to screen for breast cancer in most women even if they have dense breasts.

GPs need to be prepared to have conversations with women about breast density and their overall risk of breast cancer. This includes discussing the benefits and harms of extra screening (via ultrasound, MRI or contrast-enhanced mammograms) that can detect cancers not found on mammograms.

But even that’s not straight forward. For instance, while there is evidence extra screening will detect more cancers, there’s currently no evidence on whether it will reduce advanced-stage breast cancers or death from breast cancer.

Extra screening may lead to adverse effects such as false-positives – apparent abnormalities that, after further evaluation, are found not to be cancer.

Extra screening is also not equitable for all women due to out-of-pocket costs and limited availability through public services.

We need better pathways for evidence-based, equitable care in Australia so the benefits of notifying women about their breast density indeed outweigh any adverse consequences for women and the health system. These pathways need to be evaluated to ensure they are feasible, acceptable, effective and equitable.

Brooke Nickel, NHMRC Emerging Leader Research Fellow, University of Sydney and Nehmat Houssami, Professor of Public Health, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.