tamoxifen

Tamoxifen isn’t chemotherapy; it's a type of hormone therapy. Chemotherapy works by killing fast-growing cells in the body, including cancer cells. Tamoxifen doesn’t work that way. Instead, it works by blocking estrogen (a hormone) from targeting cancer cells. That's why it's able to treat certain hormone-sensitive (HR+) breast cancer that grows when there's estrogen around. Tamoxifen fights breast cancer by stopping estrogen from fueling the cancer.

No, Tamoxifen isn’t an aromatase inhibitor; it’s a selective estrogen receptor modulator (SERM). Aromatase inhibitors, such as anastrozole (Arimidex), stop the body from making estrogen. SERMs, like Tamoxifen, block estrogen’s effect on breast cancer cells. Both aromatase inhibitors and Tamoxifen are used to treat breast cancer. But Tamoxifen has an additional FDA-approval to lower the risk of breast cancer in females who are at high risk. Aromatase inhibitors aren't FDA-approved to lower breast cancer risk, but oncologists sometimes prescribe them off-label for this purpose because research suggests they can help as well. If you’d like to learn more about options for your specific breast cancer, talk with your oncologist.

Your care team will talk with you about how long you’ll need to take Tamoxifen. Usually, it’s recommended to take Tamoxifen or other hormone therapy for at least 5 years and sometimes up to 10 years. Don’t stop taking Tamoxifen without first talking with your oncologist.

Not everyone will have the same side effect experience with Tamoxifen, so what's considered the "worst side effects" might differ from person to person. But one of the most common side effects of Tamoxifen is hot flashes, which can be very uncomfortable. Your oncologist can give you tips to ease hot flashes, such as wearing loose-fitting layers and avoiding certain foods or drinks that might worsen hot flashes, like caffeine or spicy foods. Another bothersome side effect of Tamoxifen is having more vaginal discharge. Your oncologist might recommend you to wear cotton underwear that’s more breathable and to use panty liners in the underwear to absorb the extra discharge. Talk with your oncology team if you have questions on any specific Tamoxifen side effect or risk.

Yes, Tamoxifen can cause hair loss, but it isn’t a common side effect. When people did experience hair loss, hair thinning was more typical than complete hair loss. Talk with your oncologist if you’re concerned about hair change with Tamoxifen treatment. They can let you know about different options to help, such as using wigs, scarves, or turbans.

Tamoxifen can cause changes to the cells lining the uterus, which can raise the chance of developing uterine cancer. Although rare, studies show that people tend to have a higher risk for developing uterine cancer if they’re 50 years or older, have already started menopause, have taken Tamoxifen for a longer period of time, or are taking higher than Tamoxifen 20 mg a day. But, the National Comprehensive Cancer Network (NCCN) and American College of Obstetricians and Gynecologists (ACOG) still recommend Tamoxifen, since the benefit it offers in preventing breast cancer is still higher than the risk of developing uterine cancer. Talk with your oncologist if you have concerns about the risk of developing uterine cancer while using Tamoxifen.

In clinical studies, some people did report weight gain after starting Tamoxifen. But it's unclear whether this weight gain is caused by Tamoxifen or other factors. One possible reason for this weight gain might be swelling from fluid buildup in the arms and feet (peripheral edema), a relatively common Tamoxifen side effect. If you notice leg swelling while taking Tamoxifen, try elevating your legs or wearing compression stockings to ease the swelling. If you have more questions about how Tamoxifen might affect your weight, talk with your oncologist.