For patients with cancer, hormone therapy uses synthetic hormones or other drugs to slow or stop the growth of certain cancers by blocking the body’s natural hormones. Hormones are substances produced by glands in your body and circulated in the bloodstream. The presence of some hormones can cause certain cancers to grow. If tests show that the cancer cells contain receptors, or places where hormones can attach to drugs, surgery or radiation therapy are used to reduce the production of these hormones or block them from working. Sometimes surgery is needed to remove the gland that makes a certain hormone.
Definition of treatment
Hormone therapy, also called endocrine therapy, prevents cancer cells from getting or using the hormones they need to grow. It is a systemic therapy, meaning that the drugs or synthetic hormones travel in your bloodstream to kill cancer cells throughout the entire body. If the drugs or synthetic hormones do not work, surgery may be required to remove organs, such as the ovaries or testicles that make hormones.
Types of treatment
In women, the following drugs may be used to change hormone levels to treat breast cancer:
- Tamoxifen® and toremifene (Fareston®) is a drug given to counter the effects of estrogen and reduce the risk that breast cancer will return; it is also used to treat advanced or recurrent endometrial cancer.
- Fulvestrant (Faslodex®) is a drug that acts by destroying the estrogen receptor instead of blocking it. It often works even if the breast cancer no longer responds to tamoxifen.
Treatment for local or distant recurrent endometrial cancer depends on the amount and location of the cancer. If the recurrent cancer is extensive, hormone therapy may be recommended. Low-grade cancers containing progesterone receptors respond better to hormone therapy than higher-grade cancers and those without detectable receptors, which are unlikely to shrink during hormone therapy.
- Medroxyprogesterone acetate (Provera®) and megestrol acetate (Megace®) are drugs called progestins that work by slowing the growth of endometrial cancer cells.
- Goserelin (Zoladex®) and leuprolide (Lupron®) are gonadotropin-releasing hormone agonists; these drugs help to lower estrogen levels in women with endometrial cancer.
Surgically removing or shutting down the ovaries (ovarian ablation) to reduce or eliminate estrogen is another way to change a woman’s hormone levels, as is the use of androgens or male hormones. Letrozole (Femara®), anastrozole (Arimidex®) and exemestane (Aromasin®) are drugs called aromatase inhibitors that stop the body from producing estrogen, even after the ovaries have been removed.
In men, there are several types of hormone therapy including surgery or drugs to lower the amount of testosterone or block the body’s ability to use androgens.
- Orchiectomy is a surgical procedure to remove the testicles.
- Luteinizing hormone-releasing hormone (LHRH) analogs or agonists are drugs that lower testosterone levels, and include Degarelix (Firmagon®) and Abarelix (Plenaxis®), which is no longer available.
- Anti-androgens are drugs that make a man’s body unable to use any androgens; they may be used with orchiectomy or the LHRH analogs to provide combined androgen blockade (CAB) – a total block of all androgens produced by the body.
Hormone therapy to treat breast cancer or distant metastases in men may include Tamoxifen® for cancer that is estrogen-receptor positive, progesterone, or aromatase inhibitors to reduce the amount of estrogen
that is produced.
UC San Diego Health System expertise
Physicians at UC San Diego Health System use hormone therapy for breast, uterine sarcoma, endometrial and prostate cancer. Moores UCSD Cancer Center is currently conducting several clinical research studies to evaluate different hormonal therapies and different delivery protocols.
What is intermittent therapy?
Sometimes cancers become resistant to hormone therapy over time, so your doctor might follow an on-again, off-again approach, or intermittent therapy, when administering the drugs.
What are possible side effects of hormone therapy?
Depending upon the type of hormone therapy, side effects in women can include weight gain, hot flashes, nausea, changes in fertility, vaginal dryness, and irregular or discontinued menstrual periods. In men, hormone therapy may cause impotence, reduced sexual desire, breast growth or tenderness, bone thinning, weight gain, loss of muscle mass, fatigue, reduced mental clarity and depression.