Why you shouldn’t be alarmed by the new study about breast cancer and birth control

Birth control pills pictured in Bend, Oregon. —Ruth Fremson / The New York Times

If you’re unnerved by news of a recent study that found birth control pills containing lower levels of estrogen still raise the risk of breast cancer, a local doctor has a message for you: don’t panic.

“The small increase should not cause alarm,” said Dr. JoAnn Manson, chief of preventive medicine at Harvard’s Brigham and Women’s Hospital.

Manson was not involved in the Danish study, which was published Thursday in the New England Journal of Medicine. The researchers analyzed the health records of 1.8 million women, aged 15 to 49, in Denmark, who were tracked for a decade. They found that use of hormonal contraceptives was associated with a 20 percent increased risk of breast cancer and a 38 percent increase among women who used them for more than 10 years.


The increased risk amounts to one extra case of breast cancer per 7,690 women using the hormonal contraception per year.

“The risk of breast cancer was higher among women who currently or recently used contemporary hormonal contraceptives than among women who had never used hormonal contraceptives, and this risk increased with longer durations of use; however, absolute increases in risk were small,” researchers wrote.

Below, Manson breaks down the key points she says are important to consider about the study’s findings.

“This is a very small magnitude of increased risk”

Mason pointed out that the vast majority of the women in the study did not develop a problem and researchers did not find an increased risk of  “all-cause” mortality.

“It does demonstrate a small increase in the risk of breast cancer,” she said. “It’s a small magnitude, 20 percent increase. And with longer duration of treatment, a 38 percent increase.”

About 16 million women  in the United States and about 140 million worldwide use some type of hormonal contraception, according to the AP.

A 20 percent increase does not mean that 20 percent of women who use a hormonal contraceptive will get breast cancer, Manson said. The increase amounts to about one extra case per 8,000 users per year, she said.

“No medications are free of risk, so that’s an important concept,” she said. “The goal is to have safer and safer medications, and there are some risks associated with hormonal contraception.”

Methodological limitations


While researchers had access to information like how many children the woman had, her education level, her family history of breast cancer, they did not have access to other information on mammogram screening practices or clinical breast exams.

“Women who are taking a hormonal medication and are in the medical system having regular medical follow up visits may be having more regular breast exams by the clinician,” Mason said. “And also they may be starting mammography earlier or having more regular mammograms.”

“If there are differences in breast cancer screening, it can lead to these small increases in risk or contribute to these small increases in risk,” she said.

Benefits of hormonal contraceptives

Aside from empowering women to make reproductive choices, lower dose hormonal contraceptives have also been linked to a reduced risk of cancer of the ovaries, the uterus, and even the colon, Mason said.

The endocrinologist also pointed out that the potential alternatives to contraception — pregnancy and childbirth — have their own risks, including high hormone levels, an increased risk of blood clots, and maternal mortality during or after child birth.

Some women are higher-risk

Manson said women who already have an increased baseline risk of breast cancer due to family history or if they’re BRCA positive, for example, may want to heed the study’s findings.

Women in their 40s or older, who suffer from increased risk of breast cancer, may want to consider hormone-free contraceptive options, including IUDs that do not release hormones, having their tubes tied, or having their partner undergo a vasectomy, she said.

Major clinical changes unlikely


Manson believes very few clinicians will change their clinical practice based on these findings, though it remains to be seen whether any professional societies will want to alter recommendations and guidelines for clinicians regarding hormonal contraceptives.

“I think that very few clinicians will be changing their clinical practice based on these findings,” Manson said.

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