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Tamoxifen for breast cancer treatment
By Mayo Clinic staff
What is tamoxifen?
Tamoxifen is a synthetic hormone used to decrease the chance of recurrence in women with early-stage hormone receptor positive breast cancer. Tamoxifen is also used as a treatment for women with advanced (metastatic) hormone-sensitive breast cancer. This drug also reduces the risk of breast cancer in women who are at high risk of someday developing breast cancer.
How does tamoxifen work?
Tamoxifen belongs to a class of drugs known as selective estrogen receptor modulators. Sometimes called an anti-estrogen, tamoxifen blocks estrogen, a hormone that promotes the growth of breast cancer cells. Tamoxifen reduces your risk of breast cancer recurrence and new tumor development in your unaffected breast. It may also slow the natural loss of bone density in postmenopausal women as they age.
Who should take tamoxifen?
Tamoxifen is an adjuvant therapy option for both pre- and postmenopausal women with hormone receptor positive early-stage breast cancer.
Who shouldn't take tamoxifen?
Women who have breast cancers that aren't sensitive to estrogen get no benefit from hormonal therapies. Tamoxifen offers no benefit to women who don't carry the CYP2D6 enzyme that activates the drug, or to those who must take medicines that block this enzyme. And, generally speaking, women who have a history of blood clots shouldn't use tamoxifen.
How long should you take tamoxifen?
Usually, tamoxifen is taken daily for five years and then stopped. Research shows that survival rates are higher and recurrence rates are lower with five years of tamoxifen treatment than with a shorter term course of tamoxifen. Beyond five years, there's no convincing evidence that using tamoxifen adds benefit.
What are the side effects and health risks of tamoxifen?
Like any drug, tamoxifen may cause side effects. Most commonly, these include hot flashes, irregular periods and vaginal discharge.
Far less frequently, tamoxifen increases the risk of developing blood clots in your legs and lungs. There's also a small risk of developing cancer of the uterine lining (endometrial cancer) or the uterine muscle (uterine sarcoma).
Aromatase inhibitors for breast cancer treatment Hormone therapy for breast cancer
