Study confirms higher breast cancer risk with hormone-based contraception

Henrietta Strickland
December 7, 2017

Still, experts cautioned that the absolute risk of breast cancer for any one woman on the Pill remains very low.

In a commentary accompanying the new study, which was published in the New England Journal of Medicine, David J. Hunter, a professor of epidemiology and medicine at the University of Oxford, said the new study did not find that any modern contraceptives were risk-free.

Researchers analyzed health records of 1.8 million women, ages 15 to 49, in Denmark where a national health care system allows linking up large databases of prescription histories, cancer diagnoses and other information.

Women who now use or recently used hormone-based contraception face a 20 percent higher risk of breast cancer, although the overall risk for most women is relatively low, a new study of 1.8 million women in Denmark has concluded. Risk increased with longer use, from a 9 percent increase in risk with less than a year of contraceptive use to a 38 percent increase after more than 10 years of use.

Third-generation contraceptive pills are displayed on January 2, 2013, in Lille, in northern France.

Women who rely on birth control pills or contraceptive devices that release hormones face a small but significant increase in the risk for breast cancer, according to a large study published Wednesday (Dec 6).

Past research even suggests it protects against other types of cancer.

"Women in that age group [already] have a very low absolute risk of breast cancer", Gaudet said. "In particular the knowledge of risk with newer progestins was sparse".

It's a disappointment to doctors who had hoped that lower doses of hormones in both oral and non-pill contraceptives might be safer than older birth control pills. Dr. Charles A. Leath, a gynecologic oncologist at the University of Alabama at Birmingham, said that while this pathway was plausible, it was far from certain.

Note that the overall absolute increase was an increase of around one new breast cancer case per 7,690 current and recent users of hormonal contraception. The American Cancer Society says every year it's diagnosed in 200,000 women and a few men, and kills around 40,000. "Thus, it is not exclusively estrogen that increases the risk of breast cancer".

First, the study didn't factor in other variables like diet, physical activity, breastfeeding or alcohol consumption, which could also have an impact on developing breast cancer.

However, he noted, pretty much everything in life carries risks and women know that. "This is the first study with substantial data to show that's not the case". Unintended pregnancies cost the USA government $21 billion in 2010, according to a report from the Guttmacher Institute.

What really surprised the researchers was that the increased risk was not confined to women using oral contraceptive pills, but also was seen in women using implanted intrauterine devices, or IUDs, that contain the hormone progestin. "As with any medical intervention, hormonal contraception is associated with specific health risks".

There are also numerous potential health benefits of hormonal contraceptives beyond preventing pregnancy, including decreasing the risk of endometrial, ovarian and colorectal cancers, as well as helping with menstrual cycle regularity, migraines and acne. According to an editorial that accompanied the study in NEJM, birth control may actually be protective against cancer on the whole despite this increased risk for one type. Don't forget there is relative risk of death in pregnancy, too.

In Denmark, older women who have completed their families are most likely to use IUDs, including those containing hormones, and they are already more likely to develop breast cancer because of their age, Mørch said. Condoms and diaphragms do not deliver hormones.

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