Some of the tests done by a pathologist on your breast cancer identify whether the cancer has receptors for oestrogen (ER) or progesterone (PR). These hormones can be produced by the ovaries before menopause, and from other tissues (especially fat cells) after menopause.
About 80% of breast cancers will have oestrogen receptors – which means they are oestrogen receptor positive (ER+). About 65% of breast cancers are also progesterone receptor positive (PR+).
You can think about these receptors like little ‘docking stations’ for the hormones that float around the body. These hormones can link up with, and activate, the receptors on cancer cells to stimulate them to grow or replicate. If your breast cancer is hormone-receptor positive, you will likely be offered endocrine therapy in the form of a tablet.
The two main groups of endocrine therapy medications are called selective oestrogen receptor modulators (“SERMs”, such as tamoxifen) and aromatase inhibitors (such as anastrozole, letrozole and exemestane).
These medications work in two ways:
Endocrine therapy is not the same as Hormone Replacement Therapy (HRT). In fact, it is quite the opposite. HRT is taking oestrogen and/or progesterone to raise those hormone levels in the body to prevent the symptoms associated with menopause. If you are diagnosed with breast cancer, you should stop taking your HRT until you speak with your surgeon.
Dr Lancashire will discuss your pathology report with you and whether your breast cancer is hormone-receptor positive. He will liaise with, or may consider referring you to, an oncologist for a discussion about endocrine therapy.