Some breast cancers need estrogen or progesterone to grow, and on the surface of these cancer cells, there are “receptors”. The receptors act as potential pathways that allow hormones to enter. These are called estrogen receptor-positive (ER+) and progesterone receptor-positive (PR+) breast cancers.
How does endocrine therapy work?
Endocrine therapy prevents cancer cells from getting the hormones they need. This is the equivalent of controlling the cells so that they are starved of growth. Sometimes, these cells even shrink.
Treatment can be done with drugs, surgery, or radiation therapy, working in one of two ways:
- Reducing the amount of hormones produced by the patient.
- Blocking the receptors to make sure the hormone doesn’t get into the cancer cells.
Which patients may receive endocrine therapy?
Endocrine therapy is often recommended by doctors in the following situations.
- After removal of early-stage breast cancer to reduce the chance of breast cancer recurrence.
- Women who are at higher risk of developing breast cancer and want to reduce their risk of developing cancer use endocrine therapy to prevent developing breast cancer.
- Advanced breast cancer, which is breast cancer that has metastasized to tissue outside the breast.
What are the methods of endocrine therapy?
Endocrine therapy drugs include the following categories.
- Selective estrogen receptor modulators (SERMs), such as tamoxifen and toremifene, block the receptors on the surface of cancer cells.
- Aromatase inhibitors, including anastrozole, exemestane, and letrozole, which block the body’s adrenal glands from producing estrogen, are often used in women who have gone through menopause.
- Gonadotropin-releasing hormone (GnRH) or luteinizing hormone-releasing hormone (LH-RH) agonists, including goserelin and leuprolide, can stop the ovaries from producing estrogen.
- Fulvestrant, which alters the receptor so that it does not bind to estrogen.
Endocrine therapy is sometimes used in addition to drugs, with surgical removal of the ovaries, or radiation therapy to the ovaries, with the goal of stopping them from producing estrogen.
What are the side effects of endocrine therapy?
Side effects of drugs
Side effects depend on the medication used.
- The most common side effects of SERMs include feelings of hot flashes, mood swings, and feeling tired. These drugs may also cause blood clots, strokes, and endometrial cancer.
- Aromatase inhibitors are drugs that can cause headaches, nausea, diarrhea, joint pain, hot flashes, and a risk of weakening bones if taken for a long time.
- GnRH agonists and LH-RH agonists may cause hot flashes, mood swings, vaginal dryness, decreased sex drive, difficulty sleeping, headaches, and possibly weakened bones.
- Common side effects of fulvestrant include nausea, poor energy, and weight gain, and may also cause vomiting, diarrhea, headache, back pain, and hot flashes.
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Side effects of removal of ovaries
Oophorectomy of the ovaries can cause the patient to go into early menopause. Menopausal symptoms usually include hot flashes, vaginal dryness, frequent urination, and decreased sex drive, in addition to an increased risk of other diseases such as heart disease and osteoporosis.
After removal of the ovaries, you will not be able to get pregnant again.
Side effects of ovarian radiation therapy
The most common side effects of radiation therapy include feeling tired, skin sensitivity at the treatment site, and some people may have a decreased appetite, retching (nausea and vomiting), or other symptoms. However, these side effects are usually temporary.
How do I deal with side effects?
Some endocrine treatments can cause menopausal symptoms such as vaginal dryness, mood swings, and hot flashes. If the symptoms are mild, they can be relieved by eating healthy foods, exercising, and reducing stress.
If symptoms are severe and lifestyle changes do not work, you should consult your doctor and may be able to take medication to improve your symptoms. Some endocrine treatments can lead to weakened bones, and your doctor should be consulted about this to ensure that bone health is protected as much as possible.