MOLECULAR MARKERS OF BREAST CANCER
If breast cancer is detected through biopsy, additional tests will be done to determine the molecular makeup (or markers) of the tumour, which will help plan the best course of treatment. These tests may occur after your surgeon has removed the whole tumour for further examination.
Hormone receptor status
Hormones are chemical messengers in the body that control bodily functions. Both men and women produce the female sex hormones, oestrogen and progesterone. However, the levels are lower in men, and in women after menopause (postmenopausal women).
Hormone receptors are proteins that receive and transmit the hormone signals inside the cell. Many breast cancers have cells with hormone receptors that receive signals from oestrogen and progesterone, which may help these cancers to grow. These cancers are referred to as oestrogen receptor positive (ER+) or progesterone receptor positive (PR+) cancers. Treatment to block oestrogen or progesterone may stop these cancers from growing.
HER2 (human epithelial growth factor receptor 2) is a protein that appears on the surface of some breast cancer cells. The HER2 protein may stimulate cells to grow and divide in an uncontrolled manner. Breast cancers that have high levels of HER2 are referred to as HER2 positive (HER2+) cancers. These cancers may be treated with drugs that target HER2, such as trastuzumab (Herceptin).
Triple negative breast cancer
Breast cancers that do not have oestrogen receptors, progesterone receptors or HER2 are called triple negative breast cancers. Because they do not respond to drugs that specifically target these hormones or HER2, they are usually treated with chemotherapy. These tumours are typically more aggressive and more common among younger women diagnosed with breast cancer.
The importance of ongoing research
To further understand how the molecular makeup of tumours affect disease progression, researchers may use new classifications to identify breast cancers with a specific molecular composition. However, these classifications are generally not used to determine treatment choices.
Currently, there are still types of breast cancers for which receptors and proteins have not yet been identified. Consequently, effective and targeted treatments are yet to be developed, and research continues to play an essential role in closing this gap in our knowledge of the disease.