What is hormone therapy for breast cancer?
Hormonal therapy for breast cancer is used to treat patients who have tested positive for either estrogen and/or progesterone receptors. This is also called endocrine therapy. Blocking these hormones can prevent cancer from spreading, can prevent cancer-related deaths, and also prevent cancer from recurring.
Hormonal therapy is usually given either in neoadjuvant settings or adjuvant setting or in palliative settings . It is given before surgery (neoadjuvant hormonal therapy) to reduce the size of a tumor, or after surgery (adjuvant hormonal therapy) to reduce the risk of recurrence.
Drugs used for hormonal therapy in breast cancer treatment
Tamoxifen
Tamoxifen is a type of drug that stops the hormone estrogen from binding onto breast cancer cells. It is a selective estrogen receptor modulator (SERM) and is the principal culprit in breast tissue for breast cancer patients. It is generally prescribed in premenopausal women with breast cancer who are ER and/or PR positive. The usual dose is 20mg and it should be taken orally once a day for 5 to 10 years.
Aromatase inhibitors (AIs)
Aromatase inhibitors work by decreasing estrogen production. AIs reduce the amount of estrogen generated inside tissues (other than the ovaries) by blocking the aromatase enzyme. This enzyme is responsible for changing weak male hormones (androgens) into estrogen after the ovaries stop making estrogen (at menopause). Hence, this process only works in postmenopausal women.
Common aromatase inhibitors include:
- Anastrozole
- Exemestane
- Letrozole
Aromatase inhibitors are generally prescribed for postmenopausal women. The total duration of treatment in an adjuvant setting is 5 to 10 years.
Hormonal therapy schedules for menopausal/postmenopausal women
Women who are postmenopausal are generally prescribed hormonal therapy under the following type of schedules:
- Aromatase inhibitors for 5 years
- Starting treatment with Tamoxifen for 2 to 3 years, and then switching to an aromatase inhibitor for the next 2-3 years
- Starting treatment with Tamoxifen for 5 years, and then switching to an aromatase inhibitor for up to 5 more years (this is called extended hormonal therapy).
- Research has shown that the continuous use of Tamoxifen for up to 10 years, can significantly reduce the risk of recurrence in patients who were originally diagnosed with early breast cancer or locally advanced breast cancer.
Hormonal therapy for premenopausal women
As explained above, premenopausal women are not advised to take aromatase inhibitors, as they will not work since their ovaries are still actively producing estrogen. Their treatment schedules often include:
- Five or more years of Tamoxifen, till the time menopause begins, followed by switching to an aromatase inhibitor.
- Use of either Tamoxifen or an aromatase inhibitor, combined with the artificial suppression of ovarian function (this is one of the oldest hormone treatments for hormone receptor-positive breast cancer, and is used to stop the ovaries from making estrogen).
- Temporary menopause is induced by using medicines called gonadotropin or luteinizing releasing hormone (GnRH or LHRH) analogs. Two other medicines, namely Goserelin and Leuprolide are also injected to stop estrogen production in the ovaries for one to three months.
- Estrogen production can also be controlled for premenopausal women by surgically removing the ovaries, which is a permanent way to stop the ovaries from functioning.