Breast cancer is a disease that has many different subtypes, each with varying treatments and outcomes. The breast cancer subtypes are differentiated by the type of receptors expressed on the surface of the tumor cells. Knowing the receptor status of tumor cells is important as it helps to determine the most effective treatment.

Triple negative breast cancer (TNBC) makes up only about 10% -20%of breast cancers and is different from other types. What characterizes TNBC is the absence of certain receptor subtypes, including estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). The presence – or absence – of these receptors is determined after a biopsy is done and the sample is tested by a pathologist.

When estrogen or progesterone receptors are present in the cancer cells, the cancer is referred to as hormone positive, ER+ or PR+. Most breast cancer tumors are ER+ or PR+, and their growth is fueled by estrogen or progesterone, respectively. When HER2 is found in the cancer cells, the cancer is referred to as HER2 positive or HER2+. HER2 is a gene that is normally responsible for the growth of healthy breast tissue, but an overabundance of expressed HER2 can cause the cancer cells to rapidly grow and divide. Treatments targeted towards ER, PR, or HER2 interfere with the effects of hormones or HER2 in order to slow down or stop the growth of cancer cells. If the cancer cells lack all three receptor types, it is called triple negative breast cancer.

TNBC is different because it does not respond to hormone therapy or therapy targeted against HER2. Because TNBC does not respond to these treatments, surgery, radiation and/or chemotherapy are typically recommended. Compared to other types of breast cancer, TNBC tends to be more aggressive and has a higher recurrence in the first five years following diagnosis, but it also tends to be more responsive to chemotherapy. Women who are most at risk for TNBC include those who have the BRCA1 gene mutation and are young, African-American, and/or Hispanic.

There is extensive research focused on improving current therapies and developing new treatments for TNBC. Like any other breast cancer, prognosis and treatment efficacy depends on the size of the tumor and whether it has spread to adjacent lymph nodes. In addition to medical treatment, healthy lifestyle changes such as regular exercise, a balanced diet, and stress management can help as well.

References

1 Hamm, C. et al. (2011) A single-centre chart review exploring the adjusted association between breast cancer phenotype and prognosis. Current Oncology. Volume 18 (4).