'Triple Negative' Breast Cancer

Breast cancers are not all the same and they behave differently. To effectively target breast cancer cells with the right therapy requires that we identify the cancer subtype. By knowing the subtype and which genes the cancer expresses, we know which drugs to use, as different receptors accept different drugs.

While some subtypes lend themselves well to very specific targeted types of treatment, Triple Negative Breast Cancers (TNBCs) do not. TNBCs do, however, respond to other types of treatment. This article looks at the population that is most likely to be in the TNBC group.

Breast cancer tissue is typically tested for specific receptors to estrogen, progesterone, and human epidermal growth factor receptor 2 (her2-neu). The presence of any of these receptors, allows for targeted therapy. Targeted therapy utilizes drugs that recognize these receptors, thereby affecting only those cancer cells.

Estrogen or progesterone receptors are treated with what is called endocrine therapy. The most recognized drug used to target either of these receptors is tamoxifen. In post-menopausal women, drugs called aromastase inhibitors (Arimidex, Femara, Aromasin) perform a similar task of essentially blocking the bodies own estrogen from binding to and stimulating cancer cells that may be circulating in the body or at the site of the original tumor.

The presence of these receptors is a favorable prognostic indicator. The presence of the HER2 receptor is actually a poor prognostic indicator, suggesting a more aggressive disease. A relatively recent breakthrough in breast cancer treatment was the discovery of Herceptin, a drug that targets this receptor. While still suggesting more aggressive disease, the use of Herceptin, along with chemotherapy, has had a remarkably positive impact on the treatment of those cancers that posses this receptor.

Triple Negative Breast Cancers (TNBC), don't have any of these receptors. Thus, there is no effective targeted therapy. 10-20% of all invasive breast cancers are 'Triple Negative'. Younger women and African American women are more likely to develop this subtype of breast cancer.

In addition, women with a BRCA1 mutation are more likely to be 'triple negative'. In fact, the diagnosis of TNBC is now an indication to consider genetic testing. In addition, these subtypes of breast cancers respond differently to therapies. TNBC's tend to respond very well to chemotherapy. Thus, the indications for chemotherapy in this subgroup tends to include even small, lymph-node-negative patients.