Hormone therapy after breast cancer

Breast cancer is said hormone-dependent when the cancer cells have receptors that enable them to obtain estrogen or progesterone and be nourished by them.

Although we usually speak of hormonal therapy, it is in fact an anti-hormone therapy. After breast cancer, the goal is to block the action of hormones on cancer cells that are present or might be in order to reduce the risk of recurrence. It’s the opposite of hormone replacement therapy which aims to replace the hormones that are no longer produced. There are several medicines that are grouped according to their way of action.


Anti-estrogen drugs are blocking the receptors present on cancer cells in order to prevent them from obtaining the estrogen from which they get nourished. The rate of oestrogen in the blood is not affected.

Main anti-estrogen in first line is the Tamoxifen. He protects against osteoporosis. Among the possible side effects: hot flashes, vaginal problems, endometrial cancer (womb), nausea and vomiting, thrombosis, blood clots, weight gain etc.

Aromatase inhibitors

Aromatase inhibitors work by blocking the production of oestrogen in the body with the exception of the ovaries. The rate of oestrogen in the blood is then decreased. They are effective only in postmenopausal women.

However, it is possible to cause menopause by deleting the ovarian activity either by surgery or by medications that will be used in combination with one of the aromatase inhibitors in premenopausal women.

Main aromatase inhibitors are the letrozole (Femara), Anastrozole (Arimidex) and exemestane (Aromasin). Among their side effects: osteoporosis, vaginal dryness, muscle pain and/or joint pain, fatigue, hot flushes of heat, decreased libido, etc.

Ovarian suppression

There are several ways to stop the activities of the ovaries but the two most common are the oophorectomy (surgery to remove the ovaries) and the administration of a luteinizing hormone–releasing hormone (LHRH) agonists. The ovarian suppression can be useful especially if the woman is still not menopausal after chemotherapy and/or the tamoxifen or if the pre-menopausal woman can’t take tamoxifen.

Main LH-RH agonists are goserelin (Zoladex), leuprolide (Lupron, Lupron Depot, eligard), and buserelin (Suprefact). The main side effects are hot flushes and decreased libido.

Duration of the hormonal therapy

The duration varies depending on several factors including: the medicine, the stade and grade of cancer, tolerance to treatment. It is usually a duration of about 5 to 10 years. Some will take only Tamoxifen or one of the aromatase inhibitors. Others will start by Tamoxifen for a few years, then change to one of the aromatase inhibitors.



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