There’s no magic pill to prevent breast cancer. But there is a medicine that can help lower your risk of getting the disease or of a recurrence. Tamoxifen is one of two chemoprevention drugs that have been approved in the U.S. for breast cancer. These medications aren’t for all women, though, because they come with their own risks.
How does tamoxifen work?
Tamoxifen, also known as Nolvadex, is a type of hormone therapy that is most effective on HR+ hormone receptor-positive breast cancers, especially those that have been found early. It has been found to reduce the risk of estrogen receptor-positive breast cancer by up to 35 percent. Tamoxifen does not have the same beneficial effect on hormone-receptor-negative breast cancer because estrogen does not play the same role in that type of cancer.
HR+ breast cancer relies on hormones, specifically estrogen and progesterone, to grow. Tamoxifen works by blocking estrogen from getting to the tumor, essentially starving it of the hormone it needs to grow. It is a type of medication called a SERM (selective estrogen receptor modulator). They target select estrogen receptors, in this case, those in the breast cells.
But tamoxifen is not a one-and-done treatment. Women typically take tamoxifen in a pill or liquid form daily for five to 10 years. However, the beneficial effects can last up to 15 years after discontinuing use, according to the National Cancer Institute.
Who should consider tamoxifen for breast cancer?
Tamoxifen therapy is most commonly used to:
- Reduce the risk of a breast cancer recurrence.
- Reduce the risk of breast cancer developing in the second breast after being diagnosed in one breast.
- Shrink tumors before lumpectomy or mastectomy.
- Slow or stop the growth of HR+ breast cancer that has spread (metastasized) to other body parts.
- Have been diagnosed with ductal carcinoma in situ, which is the presence of cancer cells in a milk duct in the breast that has not spread to other breast tissue.
- Reduce the risk of breast cancer for both pre- and post-menopausal women who are at high risk based on family history, genetic testing, or other factors.
What are the risks of taking tamoxifen for breast cancer?
Taking tamoxifen has been linked to an increased risk of:
- endometrial cancer
- pulmonary embolism
- deep vein thrombosis
It can also lead to side effects such as:
- hot flashes and night sweats
- fertility problems for premenopausal women
- bone pain
- mood swings and depression
- hair thinning
Women who have had breast cancer or who are at an increased risk should discuss the pros and cons of taking tamoxifen.