Hormones are chemicals made by glands, such as the ovaries and testicles.
Hormones help some types of cancer cells grow, such as breast cancer and prostate cancer. In other cases, hormones can kill cancer cells, make cancer cells grow more slowly, or stop them from growing.
Hormone therapy as a cancer treatment may involve taking medications that interfere with the activity of the hormone or stop the body's production of the hormone. Hormone therapy may involve surgically removing a gland that is producing the hormones.
How does hormone therapy work?
If you have breast cancer, your doctor may recommend a hormone receptor test of the tumor to help determine treatment options and help learn more about the tumor. This test can help to predict whether the cancer cells are sensitive to hormones.
The hormone receptor test measures the amount of certain proteins (called hormone receptors) in cancer tissue.
Hormones that naturally occur in the body (such as estrogen and progesterone) can attach to these proteins and help them grow. If the test is positive, it is indicating that the hormone is probably helping the cancer cells to grow. In this case, hormone therapy may be given to block the way the hormone works and help keep the hormone away from the cancer cells (hormone receptors).
If the test is negative, the hormone does not affect the growth of the cancer cells, and other effective cancer treatments may be given. Always discuss the results of the hormone receptor test with your doctor.
If the test indicates that the hormones are affecting your cancer, the cancer may be treated in one of following ways:
Treating cancer cells to block the hormones they need to grow
Treating the glands that produce hormones to keep them from making hormones
Surgery to remove glands that produce the hormones, such as the ovaries that produce estrogen, or the testicles that produce testosterone
The type of hormone therapy a person receives depends on many factors, such as the type and size of the tumor, the age of the person, the presence of hormone receptors on the tumor, and other factors.
When is hormone therapy given?
Your doctor may prescribe hormone therapies before some cancer treatments or after other cancer treatments. If hormone therapy is given before the primary treatment, it is called neoadjuvant treatment.
Neoadjuvant treatments help to kill cancer cells and contribute to the effectiveness of the primary therapy, which is usually surgery. If hormone therapy is given after the primary cancer treatment, it is called adjuvant treatment. Adjuvant therapy is given to improve the chance of a cure.
With some cancers, hormone therapy is given as soon as cancer is diagnosed, and before any other treatment. It may shrink a tumor or it may halt the advance of the disease. And in some cancers, such as prostate cancer, it is helpful in relieve the painful and distressing symptoms of advanced disease. Although hormone therapy cannot cure advanced prostate cancer, it will usually shrink or halt the advance of disease, often for years.
What medications are used for hormone therapy?
Hormone therapy may be used to prevent the growth, spread, and recurrence of breast cancer. The female hormone estrogen can increase the growth of breast cancer cells in some women.
An example of this type of medication is tamoxifen, which works by blocking the effects of estrogen on the growth of malignant cells in breast tissue. However, tamoxifen does not stop the production of estrogen. Men who have breast cancer may also be treated with tamoxifen.
Tamoxifen is currently being studied as a hormone therapy for treatment of other types of cancer. There are several other hormonal agents for breast cancer that target the estrogen receptor like tamoxifen, including toremifene (Fareston) and fulvestrant (Faslodex).
Hormone therapy may be considered for women whose breast cancers test positive for estrogen or progesterone receptors.
Newer medications approved by the FDA, called aromatase inhibitors, are used to treat advanced breast cancer or prevent the recurrence of breast cancer in postmenopausal women. These drugs, such as anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin), prevent estrogen production in postmenopausal women, and may be the drug of choice for women who are past menopause.
The FDA approved the use of raloxifene (Evista) for postmenopausal women who are at high risk for breast cancer. It is also prescribed for women who have osteoporosis. Raloxifene is not for use in premenopausal women. It now joins tamoxifen as another drug that can be used to help at-risk women lower their risk of invasive breast cancer.
Fulvestrant (Faslodex), also approved by the FDA, binds with the estrogen receptor and eliminates it, rather than than just blocking it, making estrogen less effective in promoting growth of the cancer.
With prostate cancer, there may be a variety of medications used in hormone therapy. Male hormones, such as testosterone, stimulate prostate cancer to grow. Hormone therapy is given to help stop hormone production and to block the activity of the male hormones. Hormone therapy can cause a tumor to shrink and the prostate-specific antigen levels to decrease.
What are the side effects of hormone therapy?
The following are some potential side effects that may occur with hormone therapy. However, the side effects will vary depending on the type of hormone therapy that is given. Every person's hormone treatment experience is different and not every person will experience the same side effects. Discuss the potential side effects of your hormone therapy with your doctor.
As each person's individual medical profile and diagnosis is different, so is his or her reaction to treatment. Side effects may be severe, mild, or absent. Be sure to discuss possible side effects of treatment with your cancer care team before the treatment begins.
For prostate cancer, either the surgical removal of the testes or hormone drug therapy can improve the cancer. Both surgery and drugs may cause the following side effects:
For breast cancer, some women may experience side effects from tamoxifen that are similar to the symptoms some women experience in menopause. Other women do not experience any side effects when taking tamoxifen. The following are some of the side effects that may occur when taking tamoxifen:
Nausea and/or vomiting
Vaginal spotting (a blood-stained discharge from the vagina that is not part of the regular menstrual cycle)
Irregular menstrual periods
Vaginal dryness or itching and/or irritation of the skin around the vagina
Taking tamoxifen also slightly increases the risk of endometrial cancer (cancer of the lining of the uterus) and uterine sarcoma (cancer of the muscular wall of the uterus). There is also a very small risk of blood clots and stroke, eye problems such as cataracts, and liver toxicities. Tamoxifen should be avoided during pregnancy.