There are several approaches to hormone therapy.
Medications that block hormones from attaching to cancer cells
One approach to hormone therapy is to stop the hormones from attaching to the cancer cells. When the hormones can't access the cancer cells, the tumor growth may slow and the cells may die.
Breast cancer medications that have this action include:
Tamoxifen. Tamoxifen is usually taken daily in pill form. It's used to reduce the risk of cancer recurrence in women who have been treated for early-stage breast cancer. In this situation, it's typically taken for five to 10 years.
Tamoxifen may also be used to treat cancer in women with advanced cancer. Tamoxifen is appropriate for both premenopausal women and postmenopausal women.
- Toremifene (Fareston). Toremifene is taken as a daily pill. It's used to treat breast cancer that has spread to other areas of the body. Toremifene is approved for use in postmenopausal women.
- Fulvestrant (Faslodex). Fulvestrant is administered as a shot every month after first getting a dose every two weeks for six weeks. It's used in postmenopausal women to treat advanced breast cancer in situations where other hormone therapies are no longer working.
Medications that stop the body from making estrogen after menopause
Aromatase inhibitors are a class of medicines that reduce the amount of estrogen in your body, depriving breast cancer cells of the hormones they need to grow and thrive.
Aromatase inhibitors are only used in women who have undergone menopause. They cannot be used unless your body is in natural menopause or in menopause induced by medications or removal of the ovaries.
Aromatase inhibitors used to treat breast cancer include:
- Anastrozole (Arimidex). Anastrozole is used to reduce the risk of cancer recurrence in women who have been treated for early-stage breast cancer. It can also be used to treat early-stage and advanced breast cancer.
- Exemestane (Aromasin). Exemestane is used to reduce the risk of cancer recurrence in women who have been treated for early-stage breast cancer. It's sometimes used after taking tamoxifen for two or three years. It can also be used to treat advanced breast cancer in women for whom tamoxifen is no longer working.
- Letrozole (Femara). Letrozole is used to reduce the risk of cancer recurrence in women who have been treated for early-stage breast cancer. It can be used alone or given after completing tamoxifen treatment. Letrozole is also used to treat advanced breast cancer.
Aromatase inhibitors are given as pills you take once a day. How long you continue aromatase inhibitors depends on your specific situation. Current research suggests that the standard approach would be to take these medications for 10 years, but every person is different and you and your doctor should carefully assess how long you should take them.
Treatments to stop ovarian function in premenopausal women
Women who haven't undergone menopause — either naturally or as a result of cancer treatment — may opt to undergo treatment to stop their ovaries from producing hormones. These strategies are generally used in women with advanced breast cancer.
Options may include:
- Surgery to remove the ovaries (oophorectomy)
- Radiation therapy aimed at the ovaries
- Treatment with goserelin (Zoladex)
Treatments to stop ovarian function may allow premenopausal women to take medications only available to postmenopausal women.
Resistance to hormone therapies
Cancers that have spread to distant parts of your body (metastasized) that are treated with hormone-blocking therapies may become resistant to their effects over time. A new group of medications can be added to make the cancer cells respond to hormone treatments.
Two medications are currently approved for such situations:
- Palbociclib (Ibrance). Palbociclib is a pill taken daily for three out of every four weeks. Side effects include lower white blood cell count, mouth sores, rash and diarrhea. It can be used with either letrozole or fulvestrant.
- Everolimus (Afinitor). Everolimus can be used in women whose cancer has progressed while taking either anastrazole or letrozole. It is combined with and taken daily at the same time as exemestane. Side effects include mouth sores, lung problems, fatigue, rash and diarrhea.