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Even Low-Dose Contraceptives Slightly Increase Breast Cancer Risk

Dec 6, 2017
Originally published on December 7, 2017 10:22 am

It's long been known that hormonal contraception, like any medicine, carries some risks. But doctors and women have hoped that the newer generations of low-dose contraceptive pills, IUDs and implants eliminated the breast cancer risk of earlier, higher-dose formulations.

Now a big study from Denmark suggests the elevated risk of getting breast cancer — while still very small for women in their teens, 20s and 30s – holds true for these low-dose methods, too.

In the research published Wednesday in the New England Journal of Medicine, a team of scientists studied 1.8 million women between the ages of 15 and 49. They were looking to see what happened over a stretch of nearly 11 years among women who used hormonal birth control — usually a combination of estrogen and progestin — versus women who relied on non-hormonal contraceptive methods, such as a condom, diaphragm or copper IUD.

Unlike most previous research, this study didn't just track the effect of birth control pills. Because their set of data was very large, scientists this time were also able to get a good sense of the impact of various other hormonal methods — including the birth control patch, the ring, and implants as well as hormone-releasing IUDs.

The results showed it didn't much matter what sort of hormonal method was used, says Lina Morch, a research epidemiologist at the University of Copenhagen, who led the study.

Overall, Morch says, she and her colleagues found "a roughly 20 percent increased risk [of breast cancer] among women who currently use some type of hormonal contraception." And the longer the women used hormonal methods, she says, the higher their risk.

That may sound scary. But Morch and other doctors say it's important to consider how that additional risk translates in terms of actual cases of breast cancer. The illness is fairly rare among women in the age group studied.

"A 20 percent increase of a very small number is still a very small number," says Mia Gaudet, an epidemiologist with the American Cancer Society. The risk contributed by hormonal contraception, she says, is similar to the extra breast cancer risk contributed by physical inactivity, excessive weight gain in adulthood, or drinking an average of one or more alcoholic drinks per day.

"The absolute increase in risk [found in the study] is 13 per 100,000 women overall, but only 2 per 100,000 women younger than 35 years of age," writes epidemiologist David Hunter, of the University of Oxford, in an editorial accompanying the study in NEJM.

"Most of the cases that occurred in this analysis occurred among women who were using oral contraceptives in their 40s," Hunter adds.

Any additional risk of breast cancer, he says, should be weighed against the clear benefits of hormonal contraception — benefits that go beyond the obvious advantages of preventing unwanted pregnancy.

"There's very good evidence," Hunter says, "that oral contraceptives reduce the risk of ovarian cancer. They reduce the risk of endometrial cancer. And there's a strong suggestion they also reduce the risk of colorectal cancer. So, many calculations suggest that the use of oral contraceptives actually prevents more cancers than it causes."

The search for new hormonal contraceptives — methods that don't elevate breast cancer risk at all — should continue, Hunter says.

Meanwhile, a conversation with your doctor can help you figure out which contraceptive method makes most sense for you.

Copyright 2017 NPR. To see more, visit http://www.npr.org/.

MARY LOUISE KELLY, HOST:

New research finds an increased risk of breast cancer among women who are using hormonal birth control. The study's published in The New England Journal of Medicine, and NPR's Patti Neighmond has our report.

PATTI NEIGHMOND, BYLINE: Scientists have long known contraceptives that contain estrogen can increase the risk of breast cancer. But researchers in Denmark looked at 1.8 million women between the ages of 15 and 49 to see if new lower-dosed formulations are still risky. They compared what happened over nearly 11 years among women taking hormonal birth control and women using other methods. Epidemiologist Lina Morch headed the study.

LINA MORCH: We found approximately a 20 percent increased risk among women who currently use some type of hormonal contraception.

NEIGHMOND: Hormonal contraception releases estrogen, progestin or a combination of both to suppress ovulation and prevent pregnancy. Mia Gaudet with the American Cancer Society says the findings are compelling because researchers didn't just look at the birth control pill. They looked at all birth control methods that release hormones.

MIA GAUDET: Including the patch, the ring, the implant, as well as IUD.

NEIGHMOND: All of these forms of hormonal contraception increased breast cancer risk by 20 percent. And the longer women used this type of birth control, the more breast cancer risk increased. The findings are disappointing, says epidemiologist David Hunter with the University of Oxford. Over the past few decades, researchers tried to develop new hormonal formulas using less estrogen, which is known to promote breast cancer. The hope was the lower dose would decrease breast cancer risk. But that's not what this study found.

DAVID HUNTER: Unfortunately, the increase of 20 percent appears to apply to the most recent formulations just like it did in the '70s, '80s and '90s. So this tells us that things haven't changed.

NEIGHMOND: Lead researcher Morch says the findings should serve as a caution but not an alarm. A 20 percent increase translates into only one extra breast cancer case for nearly every 8,000 women. It's even lower among younger women since breast cancer in this age group is relatively rare.

MORCH: So it has to be balanced - the pros and cons of these contraceptives. And if it's not needed to take hormonal contraceptions, it might be worth considering using other methods like the copper IUD or barium if it's - like condoms, for instance.

NEIGHMOND: Now, it's important to note in the study, women over 40 were more likely to suffer breast cancer than younger women in their 20s and 30s. Age, family history and weight gain later in life all contribute to breast cancer risk. Morch suggests women over 40 discuss possible alternatives with their doctor. And epidemiologist Hunter says there are other clear benefits of hormonal contraception.

HUNTER: There's very good evidence that oral contraceptives reduce the risk of ovarian cancer. They reduce the risk of endometrial cancer. There's a strong suggestion they actually reduce the risk of colorectal cancer. And so many calculations suggest that use of all contraceptives actually prevents more cancers than it causes.

NEIGHMOND: Hunter says the search for new hormonal contraceptives that don't elevate breast cancer risk should continue. Patti Neighmond, NPR News. Transcript provided by NPR, Copyright NPR.