Sandra Ebejer, a 50-year-old who lives in Albany, New York, was diagnosed with breast cancer in late 2023. She began taking tamoxifen in March 2024, following a double mastectomy. While Ebejer doesn’t specifically remember her oncologist discussing possible side effects, her mother and some friends who have taken the drug did, so she had an idea of what they could be. However, her side effects did seem stronger than what her friends and mother reported.
“I’m already in perimenopause, so it feels almost like the tamoxifen takes your typical perimenopause symptoms and amps them up by a thousand,” Ebejer says. “Hot flashes were, by far, one of the worst things I dealt with. I literally had a day in December of last year. I was waiting for my son at the bus stop, and I’m standing with no coat on, my sleeves pushed up and sweating intensely in 15-degree weather.” She also experienced disrupted sleep, terrible mood swings, and a very dry mouth. Ebejer does feel she’s fortunate though, because despite the unpleasant side effects — especially the hot flashes — they go away after a few months, so she gets a break before they start up again.
Ebejer is one of millions of women with certain types of breast cancer who have taken tamoxifen since it was approved by the FDA in 1998. The drug lowers the risk of the cancer returning (recurrence) after they’ve had treatment. But like all medications, tamoxifen can cause side effects, and sometimes those side effects are so bothersome that people consider stopping the drug, despite the potential benefits.
Why Take Tamoxifen?
Hormone-receptor-positive breast cancer needs estrogen to grow and spread. Women make estrogen through their ovaries, and tamoxifen blocks the hormone, so it doesn’t feed into those cancer cells. This can lower the risk of the cancer returning. After menopause, the ovaries stop making estrogen. Although tamoxifen can still be used after menopause, oncologists usually first use drugs called aromatase inhibitors (AIs) instead.
Studies show that the protection you get from taking tamoxifen for five years can last as long as 15 years from when you first take it — and there’s another benefit. If you take it for the recommended time, your risk of cardiovascular disease drops, especially if you’re in your 50s.
Other people can take tamoxifen as well, like men who have early-stage ER-positive breast cancer or women who don’t have breast cancer but are at high risk of developing it.
When the Side Effects Are Severe
Many women experience some type of side effect from tamoxifen, but not all in the same way. “There is a wide spectrum of women who have side effects [from tamoxifen], says Sujatha Murali, MD, a medical oncologist at Kaiser Permanente in San Marcos, California. “Some women have a little bit here and there, but mostly they say it’s manageable.” But there’s the other side of the spectrum, she explains. “Within a week or two of starting it, they basically say, I can't live like this.”
Some of the common side effects from tamoxifen include:
- Hot flashes and night sweats — the most common, affecting about 64 % of women
- Vaginal dryness and/or discharge
- Weight gain
- Fluid retention (edema)
- Nausea
- Fatigue
- Headaches
When Murali discusses starting tamoxifen treatment with her patients, she makes sure they understand the importance of reporting side effects. “I really want to make sure there's an open dialogue with the patient because I think women minimize side effects. They don’t want to come across as complaining, or they’re incredibly worried that I’m going to take them off the drug and their breast cancer is going to come back,” she says. “But we can talk about them. So if hot flashes are your primary side effect, for example, there are medications we can use to control them.”
Should You Stay on Tamoxifen or Go Off It?
If you feel that the tamoxifen side effects are bad enough that you might consider going off the drug, you should discuss this with your doctor because there are likely other options available to you. “My approach is to decide if the side effect is serious or is it something that I can manage and help the patient tackle,” says Ankit P. Madan, MD, a medical oncologist at MedStar Health in Clinton, Maryland. “If the side effect is serious, like a blood clot or vaginal bleeding, I stop the medication. If someone has hot flashes three or four times a day, then there are medications I might try.”
According to Murali, a new medication that controls hot flashes, called fezolinetant (Veozah), has been a game changer for some of her patients, but there are also other medications, such as gabapentin and low-dose antidepressants, that could help as well.
Rather than stopping treatment altogether, some oncologists might offer a “drug holiday.” Ebejer’s doctor told her that if her symptoms got too severe, they could give her some time off and then go back on tamoxifen, giving her body a break. The is no research yet on whether taking a break from tamoxifen due to side effects affects long-term protection. But there are studies of women who temporarily stopped tamoxifen so they could get pregnant. This research suggests that there was no difference in breast cancer recurrence later.
Rather than a complete break, Murali offers struggling patients a temporary lowering of the dose. “The usual dose of tamoxifen is 20 milligrams,” she says. “Sometimes I will drop them down to 5 milligrams, have them take 5 milligrams for a couple weeks. If they're doing OK on five, go up to 10 or 5 milligrams twice a day. Then maybe try 10 milligrams twice a day. This slowly ramps up their tamoxifen dose to see if that would help with the side effects.”
Alternatives to Tamoxifen
The reason tamoxifen is so popular is its effectiveness. “Tamoxifen and endocrine therapy are a chief reason why we have achieved such improvement in hormone-positive breast cancer,” Madan says. But if you’re experiencing such severe side effects from tamoxifen that you feel you can’t continue, there are other treatments you might try, say both Murali and Madan.
For example, inducing menopause by shutting down the ovaries would stop estrogen production. Madan explains this could be done by taking medications such as goserelin (Zoladex) or leuprolide (Lupron). This would allow women to take other hormone therapies, such as AIs. “Doing bilateral oophorectomy (removing both ovaries) and using a different medication if they’re done childbearing is pretty radical, but it might be worth discussing,” he says.
Talk to Your Doctor
If you’re having side effects from tamoxifen that are interfering with your quality of life, it’s important to speak up. “We absolutely have things we can do to alleviate these side effects,” Murali says. And if the side effects are still unmanageable, there are other options.
The other thing that’s important is to know that you’re not alone. Ebejer went on Facebook to find other women who are also experiencing side effects, especially hot flashes, to learn how they deal with them. “There are a number of groups and there are women all over the world, thousands and thousands of women who are on this medication who will share their stories and share what works for them,” she says. “I think it’s a nice way of finding community and knowing that you're not alone.” Ebejer searches the groups for specific issues to see what others have said about the side effects. “And sometimes [I use them] just to not feel like I’m crazy.”
Local, in-person support groups can also be helpful. Meeting people face-to-face and forming relationships can be really helpful. You can ask your cancer treatment team for suggestions, or you can reach out to organizations like the National Breast Cancer Foundation (which has a directory of in-person and online groups), the Susan G. Komen Foundation, the American Cancer Society, CancerCare, and the Cancer Support Community.
Ebejer says she doesn’t feel she’s at that point of needing a drug break yet but would consider it. “I wouldn’t be opposed to it,” she says. “For me, the long-term goal is to just not get breast cancer again. As long as I can do that, then I’ll follow the doctor’s orders if I feel comfortable.”
