Breast density information for GPs

We are now reporting breast density to our clients and their nominated doctors.

Here you can find answers to commonly asked questions about breast density.

We continue to recommend women aged 50 to 74 have a breast screen (mammogram) every two years as it is still considered the most effective way to detect breast cancer early.

What is breast density?

Breasts are made up of a combination of tissue:

Fatty tissue

Glandular tissue

Connective/fibrous tissue

Women with high breast density have more fibroglandular tissue and less fatty tissue.

Breast density cannot be determined by the look and feel of a woman’s breast or on physical examination. It can only be measured from a mammogram.

How is breast density classified?

Breast density is commonly classified into four categories using the Breast Imaging Reporting and Data System (BI-RADS), American College of Radiology (ACR) 5th edition:

A: breasts are almost entirely fatty (approximately 10% of women)

B: breasts have scattered areas of fibroglandular tissue (approximately 40% of women)

C: breasts are heterogeneously dense. The mix of non-dense and dense tissue may hide small cancers. (approximately 40% of women)

D: breasts are extremely dense, reducing the visibility of cancers on a mammogram (approximately 10% of women)

Women with a BI-RADS category C or D classification are considered to have dense breasts. Approximately 35% of BreastScreen Victoria clients (aged 40+) have dense breasts.

Why is breast density important?

Dense breast tissue can mask the appearance of cancers in a mammogram, making them harder to detect.

High breast density also increases a person’s risk of developing breast cancer.

Women with dense breasts (BI-RADS category C or D) have a 1.5-2 times higher risk of breast cancer compared to those in BI-RADS category B. The risk is higher for women with category D density compared to category C. Breast density should be considered alongside other risk factors including age, family history and lifestyle factors including smoking and alcohol intake.

Having dense breasts does not mean that a woman will develop breast cancer or mean that a woman with breast cancer is more likely to die from it.

What influences breast density, and can it change?

Breast density usually reduces with age, with more younger women having dense breasts compared to older women. It is also influenced by other factors including genetics, BMI (a lower BMI is associated with higher breast density), having had children (may decrease breast density), hormone replacement therapy (may increase breast density), and anti-estrogen therapy (may decrease breast density).

How is breast density measured?

Breast density is measured from a mammogram. We use Volpara software to produce a measurement in a standardised, reproducible system without human variability.

No additional imaging is required to measure breast density, which means the screening process for women has not changed. No additional time or radiation is required to measure breast density.

Can everyone’s breast density be measured?

No. Volpara’s software can’t measure breast density in a small number of cases.

We won’t repeat a client’s screening if the software can’t measure their breast density as it would unnecessarily expose them to additional radiation.

What should I do if my patient has dense breasts?

Breast density should be considered in the context of a patient’s overall risk, not in isolation.

We recommend that clients with extremely dense breasts (BI-RADS category D) see a doctor for a risk assessment. You may wish to use a risk tool such as iPrevent or the Tyrer-Cuzick risk model to facilitate a discussion with your patient. While some risk factors are not modifiable, encouraging your patients to reduce their risk with lifestyle modifications is one of the key roles of GPs.

While high breast density can reduce the visibility of cancers on a mammogram, mammograms still detect the majority of cancers in people with high breast density. High breast density alone does not necessarily mean a patient needs additional imaging.

There are a range of options for enhanced surveillance for patients with high breast density including MRI, ultrasound, tomosynthesis or contrast enhanced mammography. These should be considered in the context of the patient’s other breast cancer risk factors, personal circumstances and preferences.

These supplementary tests are not currently funded as part of the BreastScreen program, however, some patients may wish to access them privately or through a public hospital. If your patient has had a mammogram in the last 12 months it is not recommended to have another mammogram (including tomosynthesis/3D mammogram) within this period due to the risk of radiation outweighing any benefit. The exception to this is if your patient has noticed any changes to their breasts since their last mammogram.

Many items are covered under the Medicare Benefits Schedule for appropriate patients. For example, for a small number of patients who meet the criteria, they will be able to access an MRI under MBS Item 63464. The criterion that may allow access for a patient with high breast density is a lifetime risk estimation greater than 30% or a 10 year absolute risk estimation greater than 5% using a clinically relevant risk evaluation algorithm. Currently, the accepted algorithm is the Tyrer-Cuzick algorithm version 8 or later, to which breast density is an input.

Case studies can be viewed in the webinar below (from 43:56). View the full webinar for more context and broader information about the BreastScreen Victoria program.