Some IUDs linked to higher rates of breast cancer, but overall risk remains low

(CNN) — A new study adds to a growing set of evidence that women who use hormonal birth control have higher rates of breast cancer, but experts have stressed that the overall risk remains low.

The latest research, published Wednesday in the medical journal JAMA, analyzed years of health records for thousands of Danish women ages 15 to 49, with an even split between those who started using intrauterine devices that release the hormone levonorgestrel for birth control and those who hadn’t used any type of hormonal contraceptive.

Among more than 150,000 women, there were about 1,600 new breast cancer diagnoses overall. But there was a 40% higher risk among women who used IUDs: about 14 additional diagnoses for every 10,000 women. The risk did not increase with duration of IUD use, the researchers said.

Earlier research has found similar links between hormonal birth control and breast cancer. The new data specifically identified risks associated with IUD use, and the findings track with the increased risk associated with oral contraceptive pills.

According to data from the US Centers for Disease Control and Prevention, more than 10% of women ages 15 to 49 in the United States currently uses an IUD or other form of long-acting reversible contraception, and about 14% use the pill. About 1 in 4 women in this age group has used an IUD at some point in their life.

When earlier research about the link between hormonal contraception use and breast cancer risk was published, the American College of Obstetricians and Gynecologists issued an advisory highlighting the importance of helping women weigh the potential risks against the benefits.

“It’s normal for people to see studies like this and feel panicked or worried, because an increase in risk of developing any kind of cancer is worrisome,” said Kelsey Hampton, director of mission communications and education for the Susan G. Komen Breast Cancer Foundation, who was not involved with the new research.

“We don’t want people to see this data and feel fear,” she said. “We want them to know that this is just more evidence and more information that they can use to have an educated conversation with their doctor.”

A report published this month by the American Cancer Society said that breast cancer deaths in the US have been falling – but new diagnoses have been rising faster among women under age 50.

That emphasizes the need for conversations about breast cancer risk to start early and happen often, Hampton said.

“When you’re making health care decisions, such as choosing what kind of birth control is right for you, that is a great opportunity to talk about your greater breast cancer risk at large,” she said.

For Dr. Eleanor Bimla Schwarz, professor of medicine at the University of California, San Francisco, the benefits of an IUD far outweigh the risks. The new data shouldn’t change the way women think about the contraception options available to them, she said.

“It reports a very small, one-in-a-thousand risk of being diagnosed with breast cancer, which is not the same as dying of breast cancer,” said Schwarz, who is also chief of general internal medicine at the San Francisco General Hospital. “That risk is really lower than many other everyday risks that women frequently take that have an impact on their breast cancer risk.”

In addition to being highly effective at preventing pregnancy, hormonal IUDs can help reduce bleeding and cramping – and there’s evidence that they may decrease a women’s risk of endometrial cancer, she said.

“I really think we have to put these conversations in context,” Schwarz said. “A breast cancer diagnosis is not the same as dying from breast cancer, and we don’t have studies that show the use of any form of hormonal contraception actually increases your risk of dying from breast cancer.”

Dr. Arif Kamal, an oncologist and chief patient officer with the American Cancer Society, noted that the new study didn’t factor in how often women were receiving mammograms.

Women with IUDs could be interacting with their doctors more often and therefore be more likely to have screenings that lead to diagnoses, he said.

But for those women who are at higher risk of breast cancer or are otherwise concerned about the potential risks associated with hormonal birth control, it’s important to know that other options exist, he said – including copper IUDs that are just as effective and not associated with any risk.

“There’s not a one-size-fits-all approach,” Kamal said. “A person’s risk of breast cancer and their underlying anxiety or worry about breast cancer should inform a decision that’s made between a woman and her doctor about what’s the right thing to do.”

And there are many other lifestyle factors that women can control to reduce their risk of breast cancer, such as getting more exercise and limiting alcohol intake, experts say.

“The goal is for people to make informed decisions and not to be scared out of considering things that might be good for you,” Schwarz said. “Especially in states that don’t have access to abortion services right now, the last thing we want is for somebody to be scared of using an IUD and go have a permanent [sterilization] surgery and then regret it.”

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