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Endocrine Therapy

Some of the tests done by a pathologist on your breast cancer are to identify if they have any 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, then it is likely that you will be recommended endocrine therapy in the form of a tablet.

The two main groups of endocrine therapy medications are called selective oestrogen receptor modulators (“SERMs”, which includes tamoxifen) and aromatase inhibitors (which includes anastrozole, letrozole and exemestane).

These tablets work in two ways:

  • To lower the amount of oestrogen in the body
  • To block the receptors for oestrogen on cancer cells

It is very important to know that 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 in order 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 or not 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.

Follow the following links below for more on breast cancer management:

Breast conserving surgery


Axillary surgery

Oncoplastic breast surgery

Prophylactic mastectomy

Breast Reconstruction


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