A new study has linked IUDs to 'higher breast cancer risk'. Here's what you need to know.

Over the past week or so, it’s likely you would have come across headlines linking hormonal contraception to breast cancer.

These stories were sparked by a large, Danish study published in The New England Journal of Medicine, which found a slightly higher number of breast cancer cases among women who use hormone-based birth control methods, including the pill, implants and intrauterine devices.

While the findings are significant, many medical professionals have expressed concern that it may cause unnecessary alarm among women.

So is there reason to worry? Or has this research been over-blown? Here’s what you need to know.

Why is this study such a big deal?

While the link between breast cancer and hormonal contraceptives has been reported for years, this study is the first to examine the risks associated with modern, lower-dose formulations in a large number of people. (By large, we mean 1.8 million Danes aged between 15 and 49, all of whom were followed over the course of a decade.)

Also significant, is the fact that the study included ‘long-acting reversible contraceptives’ (LARCs), namely implants and IUDs, and found that there is minimal difference in the risk posed by each.

As American oncologist Dr Marisa Weiss summarised to The New York Times, “This is an important study because we had no idea how the modern day pills compared to the old-fashioned pills in terms of breast cancer risk, and we didn’t know anything about IUDs… Gynaecologists just assumed that a lower dose of hormone meant a lower risk of cancer. But [the study shows that] the same elevated risk is there.”


What kind of risk?

That depends on a variety of factors, including age and duration of use, but as the study itself noted that “absolute increases in risk were small”: “approximately one extra breast cancer for every 7690 women using hormonal contraception for one year”.

For women 35 or younger, it was only one extra case for every 50,000.

Speaking to Mamamia, Dr Charlotte Elder, fellow of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, said it’s important for women to balance these slight risks against the many benefits associated with hormonal contraception. Among them, reduced likelihood of developing more deadly cancers including bowel and ovarian.

“The overall picture is that, yes, we know that some hormonal contraceptives in some women can slightly increase the risk of breast cancer. But if you look at women who use hormonal contraceptives, the overall risk is probably tipped toward less cancer and less death from cancer,” she said.

Tina Harris talks about managing family time while living with breast cancer. (Post continues below.)

It’s important to note, that there are limitations to the study, too.


The authors themselves, for example, conceded that they could not take into account factors like physical activity, breast feeding and alcohol consumption, which may also influence breast cancer risk.

Also, as a trio of University of California specialists wrote to The New York Times, the study didn’t factor in that “clinical visits to obtain a prescription contraceptive increase opportunities to diagnose breast cancer”.

Still, Dr Elder welcomes continuing research in this area.

“Should we keep looking at contraceptives and designing better ones? Yes, absolutely. But I think the concept that some hormonal contraceptives ever so slightly increase the risk of breast cancer should not be a reason for people to stop using theirs,” she said.

“Hormonal contraceptives available in Australia are safe and reliable, and we see significant complications very rarely.”

Still, I’m concerned. What should I do?

It’s important you feel comfortable with your choice of contraceptive, so Dr Elder urges anyone with questions or concerns to speak to their doctor.

“There’s no need to be worried about this [study]. But of course, if you are, pop in to see your GP, have a chat, talk about your specific circumstances, talk about the specific contraceptive you’re taking or thinking of taking, and think about all of the pros and cons,” she said.