What is triple-negative breast cancer?

About 10 to 20 percent of breast cancers are triple-negative.

Knowing breast cancer basics can help you understand how triple-negative breast cancer is different from other types of breast cancer. Doctors search for the presence or absence of three receptors, proteins that live inside or on the surface of a cell and bind to something in the body to cause the cell to react. You may have heard of the oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2).

In oestrogen receptor-positive breast cancer, progesterone receptor-positive breast cancer and HER2 positive breast cancer, treatments prevent, slow or stop cancer growth with medicines that target those receptors. But triple-negative breast cancers need different types of treatments because they are oestrogen receptor negative, progesterone receptor negative and HER2 negative. Medicines like tamoxifen, which targets the oestrogen receptor, and trastuzumab (Herceptin), which targets HER2, are not helpful in treating triple-negative breast cancer. Instead, chemotherapy has been shown to be the most effective treatment for triple-negative breast cancer.

Researchers are working to improve their understanding of the biology of triple-negative breast cancers, how these types of cancers behave and what puts people at risk for them. Their goals are to find out the best ways to use treatments that already exist and to develop new ones.

Understanding the ‘Basal-like’ Subtype

Most triple-negative breast cancers have a basal-like cell pattern. This term means the cells look like the basal cells that line the breast ducts, the tubes in the breast where milk travels.

Basal-like breast cancers tend to over express, or make too much of, certain genes that encourage cancer growth. Not all triple-negative breast cancers are basal-like, and not all basal-like breast cancers are triple-negative. About 70 to 90 percent of triple-negative breast cancers are basal-like.

Doctors choose treatments because the cancer is triple-negative, not because it is basal-like. The basal status of the cancer does not factor into treatment decisions.

Myth About Triple-Negative Breast Cancer

MYTH – Women with triple-negative breast cancer can have the same treatments as all other women with breast cancer.

FACT – Many people do not understand that there are different kinds of breast cancer. Even some women who have had breast cancer do not understand the differences between triple negative breast cancers and breast cancers that are hormone receptor-positive or HER2 positive.

Researchers are still learning why some women are more likely than others to develop triple-negative breast cancer. Research supports a relationship between risk and your genes, age, race and ethnicity.

Breast Cancer Gene Mutations

Everyone has BRCA1 and BRCA2 genes, which we get from our mother and father. When they work properly, these genes prevent the development of cancers. However, less than 10 percent of people with breast cancer are born with a mutation, or abnormality, in BRCA1 or BRCA2.

Triple-Negative Breast Cancer Risk Factors

If you are born with a BRCA1 or BRCA2 gene mutation, you are at increased risk for developing breast, ovarian and other cancers throughout your life. The BRCA1 mutation puts you at higher risk for developing a basal-like breast cancer. Scientists are still trying to find out why BRCA1 mutations increase the risk of developing triple-negative breast cancer. Keep in mind, not all breast cancers from BRCA mutations are triple-negative. In fact, BRCA2 mutations are more likely to be present in oestrogen receptor-positive breast cancer.  If you have a family history of breast cancer, you and your relatives could carry a BRCA1 or BRCA2 mutation. You could also be the first person in your family known to develop breast cancer because of a BRCA mutation. Knowing your BRCA status can help you and your doctors discuss an effective treatment plan and learn ways to reduce your risk for recurrence. A genetic counsellor can talk with you about genetic testing. Anna was tested and was NOT BRCA positive, but this is important information which can affect treatment options.

Age, Race or Ethnicity

Several studies suggest that being premenopausal, African-American, Latina or Caribbean increases  risk of developing basal-like or triple-negative breast cancer. Among African-American women who develop breast cancer, there is an estimated 20 to 40 percent chance of the breast cancer being triple-negative. Researchers do not yet understand why premenopausal women and women in some ethnic groups have higher rates of triple negative breast cancer.

Resources for more information:

www.tnbcfoundation.org

www.triplenegative.co.uk