Fear of side effects is keeping women from taking the breast cancer prevention drug, despite its effectiveness.

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Medical professionals say the benefits of tamoxifen are usually worth the potential side effects. Getty Images

After 18 months of treatment for breast cancer, Tammy Salamone was ready to get on with her life.

To lower the chances of recurrence, her oncologist prescribed the drug tamoxifen. She’d have to take it for 5 to 10 years.

The California resident chose not to take it at all.

She’s not alone.

A new study published in Clinical Breast Cancer finds that many women in the United Kingdom don’t want to take the drug either.

Tamoxifen is a selective estrogen receptor modulator (SERM) used to treat hormone receptor-positive breast cancer and to prevent risk of recurrence.

It’s also used to help lower the risk of breast cancer in women who haven’t been diagnosed but are considered high risk.

The multicenter study focused on women with a higher than average risk who were seeking breast cancer prevention.

More than 400 women completed a baseline survey following an appointment to discuss their risk.

More than 72 percent were concerned about long-term effects of tamoxifen, and more than 61 percent said taking the drug would worry them.

Almost 57 percent believed tamoxifen would give them unpleasant side effects. More than 22 percent said tamoxifen was a “mystery” to them.

About 29 percent said doctors use too many medicines. More than 35 percent said if doctors spent more time with patients, they’d prescribe fewer drugs.

Of the 258 who provided data at least three months later, less than 15 percent were taking tamoxifen.

Dr. Robert Wesolowski, assistant professor at the Ohio State University Comprehensive Cancer Center, told Healthline that roughly 1.3 million women receive breast cancer diagnoses worldwide every year.

“Considering its effectiveness in preventing recurrence of hormone receptor-positive breast cancer, tamoxifen has saved lives of millions of women around the globe since it has been approved in [the] 1970s,” he said.

For breast cancer prevention, people are usually advised to take tamoxifen for five years.

It’s also prescribed for five years for most patients with early stage, low-risk estrogen receptor-positive breast cancer. For those at higher risk, it can be taken as long as 10 years.

Those with metastatic breast cancer can typically take it as long as it’s controlling the cancer, Wesolowski says.

Other studies have found that women who have received breast cancer diagnoses also have issues with the drug.

Research presented at the European Society for Medical Oncology 2018 Congress found that more that 18 percent of premenopausal women with early stage hormone receptor-positive breast cancer weren’t taking hormonal therapy as prescribed.

Of those, 13 percent weren’t taking any.

Doctors are concerned.

The lead author of that study said taking less than 80 percent of prescribed treatment can shorten time to recurrence and raise the risk of death.

“There are serious side effects of tamoxifen, but fortunately, they are quite rare,” Wesolowski said.

Some of the side effects include hot flashes, mood swings, vaginal dryness, discharge, and slight weight gain.

Wesolowski says less common side effects include allergic reaction, increased risk of blood clots in about 1 percent of patients, and a small risk of endometrial cancer.

“That can be a serious problem. This occurred in about 1 to 2 percent of patients who are on tamoxifen for five years. Fortunately, most cases of endometrial cancer turned out to be in early stage and curable. Very rarely, tamoxifen can cause increase in calcium levels, which occurs in less than 1 percent of patients,” he explained.

A 2015 study published in the Journal of the National Cancer Institute found that in addition to side effects, many premenopausal women had fertility concerns.

Wesolowski says that although many premenopausal women stop having periods while taking tamoxifen, it doesn’t necessarily mean they can’t get pregnant.

According to BreastCancer.org, other side effects can include headache, depression, thinning hair, constipation, dry skin, and loss of libido.

Women who have a history of endometrial cancer, blood clots, and strokes should avoid tamoxifen, advises Wesolowski. For those women, there are other anti-estrogen therapies.

All treatments for breast cancer have risks, he says.

“Tamoxifen, for example, has far less risks than chemotherapy. Tamoxifen is an effective and most appropriate agent for some women with breast cancer. But other forms of breast cancer treatment exist and can be more appropriate than tamoxifen for some women as well. It is best to discuss available treatment options, including their risks, benefits, and alternatives with the oncologist,” Wesolowski said.

For some women, it’s a quality of life issue.

After two surgeries, 12 weeks of chemotherapy, and one year of infusions every three weeks, Salamone wanted it to end.

“I had heard firsthand from many women about the horrible side effects. Mainly, weight gain of 10 to 15 pounds, low sex drive, terrible muscle and body aches, to name a few,” she told Healthline.

“And tamoxifen is listed on the American Cancer Society (ACS) as a group 1 carcinogen, along with a lot of other things I don’t want to put into my body,” she explained.

Under that listing, the ACS website notes, “There is also conclusive evidence that tamoxifen reduces the risk of contralateral breast cancer in breast cancer patients.”

Salamone, a personal trainer specializing in breast cancer recovery, says her oncologist brought it up at every appointment. But since the cancer was caught early, she didn’t push the issue.

“My husband and girls are very supportive because they saw how difficult the treatment was for me and want their wife and mom back. I really haven’t told very many other people. When they ask if I’m done with treatment, I say yes, and leave it at that,” she said.

For other women, side effects are quite tolerable.

Nancy Hand of California has been taking tamoxifen for 14 months.

“The only side effect I’ve noticed is hot flashes. I was moved from hormone replacement to hormone blocking, so the first couple of months were dreadful. It’s since leveled off to a more manageable level,” she told Healthline.

Her oncologist has talked to her about switching from tamoxifen to an aromatase inhibitor in a couple of years.

“But the tamoxifen has been so easy, I’m not real eager to switch,” she said.

Wesolowski advises that benefits of taking the drug need to be carefully weighed against risks.

“In general, tamoxifen for five years reduces the probability of breast cancer recurrence by almost 50 percent, while risks of serious side effects are at around 1 percent or less,” he explained.

“In most patients with hormone receptor-positive breast cancer, the benefits are far greater than the risks,” Wesolowski said.