Estrogen encourages the growth of two out of three breast cancers, says the American Cancer Society. These cancers are known as estrogen-receptor or progesterone-receptor positive cancers. To effectively treat these kinds of cancers, therapies target those receptors and aim to limit or eliminate the effects of estrogen, as well as lower the overall estrogen levels in the body.
Aromatase Inhibitors
Aromatase inhibitors prevent the body from making estrogen, says the American Cancer Society. These drugs are only given to post-menopausal women whose cancers are estrogen-receptor positive, typically as a daily pill. Drugs in this category include anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara), as listed by breastcancer.org. These medications can be used after using tamoxifen or in place of tamoxifen, since tamoxifen has more negative side effects. Side effects of these drugs can include heart problems, bone loss and joint stiffness or pain.
Selective Estrogen Receptor Modulators
Selective estrogen receptor modulators, also known as SERMs, are drugs that interact with estrogen receptors. These medications can differentiate between different types of estrogen receptors and acts of various tissues differently; human estrogen affects many tissues in the same way, whereas SERMs do not, according to the American Association for Cancer Research. For estrogen receptor-positive cancer, SERMs bind to the estrogen receptors, preventing human estrogen from activating them. Tamoxifen (Nolvadex) and raloxifene (Evista) are two well-known SERMs. Side effects that the American Association for Cancer Research lists include hot flashes, menstrual irregularities, headaches, fatigue and vaginal irritation. There is also an increased risk of endometrial cancer, pulmonary embolism and cataracts.
Estrogen Receptor Down Regulators
Fulvestrant (brand name Faslodex) is a drug known as an estrogen receptor down regulator, says Chemocare.com. This class of drugs attaches to the estrogen receptors instead of estrogen, then breaks down the receptors so the cells do not respond to estrogen anymore. Side effects of the medication can include hot flashes, nausea, vomiting, diarrhea, abdominal or back pain and pain at the injection site, according to Breastcancer.org.
Ovarian Ablation
Ovarian ablation is another option to treat estrogen-receptor positive cancers. The American Cancer Society says that in pre-menopausal women, surgically removing or using medication to shut down the ovaries removes the main source of estrogen. This puts a woman into direct menopause and can cause side effects like hot flashes, vaginal dryness, night sweats and mood swings.
