Some breast cancers need the hormones estrogen or progesterone to grow. These cancer cells have "receptors" on their surface that let hormones in. One type is called estrogen-receptor-positive (ER+) breast cancer. Another type is called progesterone-receptor-positive (PR+) breast cancer.
Hormone treatment keeps these cancers from getting the hormones they need. It's like starving the cancer cells so that they stop growing. And the tumor sometimes shrinks.
Treatment works in one of two ways:
- It lowers the amount of hormones your body makes.
- It blocks the cell receptors. This keeps the hormones from getting inside to feed the cancer cells.
Types of hormone treatment
Medicines used for hormone treatment include:
- Selective estrogen receptor modulators (SERMs). They block the cell receptors from letting in hormones. They include:
- Tamoxifen (Nolvadex).
- Toremifene (Fareston).
- Aromatase inhibitors. These block the enzyme aromatase, which converts other hormones to estrogen. They are used mostly in women who are past menopause. They include:
- Anastrozole (Arimidex).
- Exemestane (Aromasin).
- Letrozole (Femara).
- GnRH agonists or LH-RH agonists. They stop your ovaries from making estrogen. They include:
- Goserelin (Zoladex).
- Leuprolide (Lupron).
- Fulvestrant (Faslodex). This drug changes the receptors so that they can't take in estrogen.
Sometimes the ovaries are removed with surgery or treated with radiation. This is done to stop the ovaries from making estrogen.
Side effects of treatment
The side effects of hormone treatment depend on the drug that is used.
- Selective estrogen receptor modulators (SERMS).
The most common side effects are hot flashes, mood swings, and feeling very tired. These drugs may also raise your risk for blood clots, stroke, and endometrial cancer.
- Aromatase inhibitors.
These can cause headaches, nausea, diarrhea, aching joints, and hot flashes. Using these medicines for a long time may cause bone thinning.
- GnRH agonists and LH-RH agonists.
These drugs can cause hot flashes, mood swings, and vaginal dryness. They can cause less interest in sex, trouble sleeping, and headaches. Risks also include bone thinning.
Common side effects include nausea, lack of energy, and weight gain. It may also cause vomiting, diarrhea, headache, back pain, and hot flashes.
Side effects of surgery
Removing your ovaries makes you start menopause, if you haven't started it yet. Menopause often has symptoms like hot flashes, vaginal dryness, urinating often, and having less interest in sex. And it raises your risk for other diseases, like heart disease and osteoporosis.
When your ovaries are removed, you can no longer get pregnant.
Managing side effects
If symptoms—like vaginal dryness, mood swings, and hot flashes—are mild, you may get some relief if you eat healthy foods, exercise, and lower your stress. Your doctor may recommend medicine for severe symptoms. Ask your doctor about ways to protect your bones if they're thinning because of treatment.