the importance of knowing your breast density

Breast density & cancer risk: what women need to know

With new research emerging that suggests breast density is a key predictor of a woman’s breast cancer risk, knowing your breast density is becoming increasingly important to your overall breast awareness and health.

What is breast density?

Breast density compares the amount of fat to the amount of tissue, as seen on a mammogram. Breasts are made up of fat and breast tissue, including glandular and connective tissues. Higher breast density therefore means there is a greater amount of breast and connective tissue in comparison to fat.

In general, pre-menopausal women tend to have denser breast tissue, and breast density typically decreases as women get older. Denser breasts are very common; approximately 40 per cent of women over the age of 40 have what is considered “dense” breast tissue.

It’s important to note that breast density is not a measure of how the breasts feel, but rather how the breasts look on a mammogram.

Why is breast density important?

Mounting evidence suggests that breast density is an important factor in not only a woman’s risk of breast cancer, but also in the detection of breast cancer tumors.

Research shows that women with dense breasts are four to six times more likely to be diagnosed with breast cancer than women who demonstrate little or no density. To put this into context, this means that women with higher breast density are at a greater risk than those who have a family history of breast cancer – a factor which almost doubles your risk if a member of your immediate family has been previously diagnosed.

To make matters worse, tumor detection can be that much more difficult for women with dense breasts, putting them at a further disadvantage during routine mammograms. On a mammogram, cancers and dense breast tissue can both appear either white or light grey, making it very difficult for a radiologist to pick out a cancer within the normal dense tissue. Studies have shown that in women with dense breasts, up to 50 per cent of cancers are missed on mammograms.

Screening mammograms are still effective in identifying most types of cancer in early stages. Like all screening tests, however, they aren’t perfect. Radiologists must use a specialized screening test called tomosynthesis (or 3D mammography), together with an ultrasound, to screen dense breast tissue adequately. This testing is not done routinely in British Columbia, due to both legislation and costs. However, in Alberta, a breast density measure is standard on a mammogram.

How can I tell if my breasts are dense?

Unfortunately, you and your physician cannot tell if you have dense breast tissue through a physical exam alone. The truth is, it takes a mammogram and a well-trained radiologist to report accurately on your breast density.

Unlike Alberta, where breast density is reported with your mammogram, in British Columbia, no screening guidelines currently exist that are applicable specifically to women with dense breasts. Regular screening mammograms, which start at age 40 and occur every two years, will not report the density of your breasts. Therefore, health care providers do not routinely use a woman’s breast density to assess her risk of breast cancer.

As more research is conducted, individualized screening recommendations for breast cancer may eventually replace current ones, and doctors may begin using breast density to assess cancer risk in the near future.

You can, however, contact your doctor to obtain more information. You or your family physician can download a request form here from the British Columbia Cancer Agency to learn more about your breast tissue density.

What can I do if I have dense breasts?

If you determine that you have high-density breast tissue, additional screening methods (such as an ultrasound or 3D screening) may be recommended in addition to a regular mammogram. If you have additional risk factors for breast cancer – such as a family history, past biopsy or chest radiation – an MRI may also be recommended.

If you have any questions about your breast density, please speak with your Copeman physician during your next appointment.

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