Study Finds Small Breast Cancer Risk Linked with Today’s Hormonal Birth Control

close up of a circular pack of birth control pills

A study of Danish women finds that newer forms of contraceptives, including birth control pills and hormone-releasing IUDs, increase the risk of breast cancer about as much as older forms of hormonal contraceptives – about 20%. Studies have long shown that hormonal birth control slightly raises breast cancer risk. But newer contraceptives contain less of the hormone drugs estradiol and progestin, and it was hoped that they would not increase breast cancer risk as much.

The study was published December 6 in the New England Journal of Medicine.

Researchers from the University of Copenhagen looked at the records of all the women in Denmark between the ages of 15 and 49. They followed 1.8 million women for almost 11 years to compare those who had used contraception to those who hadn’t, and see how many of them were diagnosed with breast cancer. Overall, they found that women who used hormonal contraception had about a 20% higher risk of breast cancer than women who had never used hormonal contraception.

The average age of women in the study was 35. The risk of breast cancer at this age is low; therefore, even when the risk increases by 20%, a woman’s overall risk is still low. According to the study, the increased risk equates to 1 extra breast cancer diagnosis for every 7,690 women using hormonal contraceptives for 1 year. For each year a woman used hormonal contraceptives, her risk increased a little more. And even after she stopped using them, the risk of breast cancer was still higher among women who had used contraceptives for 5 years or more than among women who had never used them. The increased risk remained for at least 5 to 10 years.

Interpreting the findings

According to Mia Gaudet, American Cancer Society’s Strategic Director, Breast and Gynecologic Cancer Research, the findings don’t necessarily mean that women should stop using hormonal contraceptives. She says:

  1. Women need to balance their immediate needs with long-term risk. They should also take into consideration that older studies have linked hormonal contraceptives to a lower risk of getting ovarian, endometrial, and colorectal cancers later in life. Women may want to have a discussion about the benefits and risks of hormonal contraceptives with their doctor.
  2. The study findings show a small increased risk among women who are already at a relatively low risk of getting breast cancer.
  3. It has long been known that hormonal contraceptives were linked with an increased risk of breast cancer. The information from this latest study is not any different from the information women already had when they made the decision to use hormonal contraceptives.

Lifestyle changes can lower your risk for breast cancer

Gaudet says women who want to lower their risk for breast cancer can make other lifestyle changes. They include:

  1. Watching your weight. Being overweight or obese increases breast cancer risk. This is especially true after menopause and for women who gain weight as adults. After menopause, most of your estrogen comes from fat tissue. Having more fat tissue can increase your chance of getting breast cancer by raising estrogen levels. Also, women who are overweight tend to have higher levels of insulin, another hormone. Higher insulin levels have also been linked to some cancers, including breast cancer.
  2. Exercising regularly. Many studies have found that exercise is a breast-healthy habit. The American Cancer Society recommends getting at least 150 minutes of moderate-intensity activity or 75 minutes of vigorous activity each week. (Or a combination of both.) Moderate-intensity activities are at the level of a brisk walk that makes you breathe hard.
  3. Limiting time spent sitting. Evidence is growing that sitting time increases the likelihood of developing cancer, especially for women. In an American Cancer Society study, women who spent 6 hours or more each a day sitting when not working had a 10% greater risk for invasive breast cancer and an increased risk for other cancer types as well, compared with women who sat less than 3 hours a day.
  4. Limiting alcohol. Research has shown that women who have 2 to 3 alcohol drinks a day have about a 20% higher risk compared to women who don’t drink at all. Women who have 1 drink a day have a very small increase in risk. Excessive drinking increases the risk of other cancer types, too. The American Cancer Society recommends women have no more than 1 alcohol drink in a single day. A drink is 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of hard liquor.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Contemporary Hormonal Contraception and the Risk of Breast Cancer. Published December 6, 2017 in the New England Journal of Medicine. First author Lina S. Mørch, PhD, University of Copenhagen.


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