BREASTSCREEN AUSTRALIA IS NOW REPORTING MY BREAST DENSITY: WHY AND WHAT DOES IT MEAN FOR ME?

Understanding breast density

You may have noticed that your mammogram report looks slightly different now.  It doesn’t just say “normal”. It also categorises your breast density into 1 of 4 categories.

What does this mean?

Breast density refers to the glandular tissue in your breast such as skin, blood vessels, ducts and fibrous tissue. It appears white on a mammogram or x-ray.  Breast tissue is also made up of non-dense tissue or fatty tissue which is also white on mammograms.

Breast density matters for two reasons.

1.      Cancer is also dense and appears white on a mammogram so, on a mammogram of a very dense breast, cancer is hard to see.

2.      Having higher density breasts can slightly increase the risk of developing breast cancer.  It is not, however, associated with a higher mortality from breast cancer.

This does not mean you are going to get breast cancer, but it is worth understanding your individual risk.

Currently, BreastScreen Australia routinely measures breast density, and then notifies women of their breast density.  Another step, which unfortunately has not been realised yet, will be the development of guidelines to provide tailored follow up or additional imaging options like ultrasound or MRI for those with higher breast density.

The aim of this will be to improve early detection of breast cancer, reduce the need for more invasive and extensive treatments, and improve breast cancer survival rates.

How do we define breast density?

Breast density is defined as the amount of radio-opaque or white elements compared to radiolucent or black fat on the image. It is a radiological finding measured by the radiologist and does not always correlate with clinical examination or what you feel in your breasts.

Having radiologically dense breasts is common, occurring in ~50% of the population.

There are many ways to report mammographic breast density but the most common method and the method being used by BreastScreen Australia is the BI-RADS classification. It is based on a scale where the radiologist looks at the image and gives the breast a score as below:

A – almost entirely fatty (dark)

B – scattered areas of fibroglandular density (very dark)

C – heterogeneously dense (very white)

D – extremely dense (white)

‘Dense breasts’ typically refers to category C and D.

It is important to note that a woman’s breast density can fluctuate over time, e.g. during their menstrual cycle, with weight changes, before and after they go through menopause, and if they are taking hormones such as the pill or HRT.  Breast density will be lower in post-menopausal women as traditionally their breast composition becomes fattier with the loss of oestrogen and fibrous tissue after menopause. Because the BI-RADS classification relies on a radiologist to decide the density, sometimes there can be interpreter discrepancies as well. 

What exactly is the risk if I have ‘dense breasts’? And how worried should I be?

While increased breast density is a risk factor for breast cancer, the extent to which breast density affects risk is not absolutely established.  What is important to remember is that breast density is just one of the risk factors for breast cancer.  What we need to do is look at women as a whole and consider their other risk factors as well as breast density. These other risk factors include:

• Ethnic background

• Family history of breast cancer

• Overweight or obese

• Sedentary lifestyle

• Smoking

• Age at first conception

• Breastfeeding

• Age of first period

• Age at menopause

• Exposure to oestrogen e.g. did they take the pill?

OK, I have ‘dense breasts’. What’s next?

In Australia, the recommendation for Women with Dense Breasts is:

1.      Routine Screening Recommendations

a.      Women aged 50 – 74 years – mammogram every 2 years via BreastScreen Australia

b.     Women aged 40 – 49 years and 75+ years: eligible for mammogram with BreastScreen Australia but not actively invited

2.      Current Clinical Practice (not mandated)

a.      See your GP to calculate breast cancer risk using tools like iPrevent by the National Breast Cancer Foundation

b.     Discuss whether you would like to consider additional imaging such as ultrasound, 3D tomography imaging (mammogram) or MRI.

c.      Discuss whether you would like to increase the frequency of your mammograms, e.g. annual rather than biennial.

d.     These decisions are made case-by-case between patients and their doctors.

3.      Australia often tends to follow the US in terms of our guidelines.  Currently, in the US, recommendations are as below.  These are guidelines but not mandated.

Things to consider about the extra imaging modalities 

·         Mammograms (2D) as provided by BreastScreen Australia are still considered to be appropriate for screening for breast cancer for Australian women, including women with dense breasts.

·         The recommendation for women of all breast density categories is every 2 years.

·         It is felt that 15-20% of breast cancer may be missing on 2D mammogram if a woman has ‘dense breasts’.

·         3D tomography is more reliable and accurate, improves cancer detection and is increasingly becoming standard.

·         Ultrasound is a great form of imaging as there is no radiation and it’s easily available.  It is, however, known to have a high rate of false positives which can cause a lot of stress.

·         MRI is extremely sensitive but expensive and requires contrast. It is only recommended for women who have dense breasts and high risk of breast cancer as calculated by a breast cancer tool, or who have a breast cancer gene such as BRCA.

Take-home messages

In Australia, the current national breast screening guidelines are provided by BreastScreen Australia and the Royal Australian and New Zealand College of Radiologists (RANZCR). However, there is no specific national guideline for management of women with increased breast density.

The approach that we chose to take is to recognise that breast density can have an impact on cancer risk and mammographic accuracy. Whilst BreastScreen Australia mammograms are the 1st line screening tool, if you return a category C or D breast density, we will want to discuss with you your overall risk of developing breast cancer and whether supplemental imaging should be considered. It will be a decision for you and your doctor.