Do Hormonal Contraceptives Increase Breast Cancer Risk?

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According to a Danish study, contraceptives that use hormones, including birth control pills and intrauterine devices (IUDs), slightly increase the risk of breast cancer. But the importance of the increase is unique to each woman and depends on many factors, including:

  • her age
  • her general health
  • her personal risk of breast cancer
  • other breast cancer risk factors, such as smoking cigarettes, drinking alcohol, and maintaining a healthy weight

The study was published on Dec. 7, 2017 by the New England Journal of Medicine. Read the abstract of “Contemporary Hormonal Contraception and the Risk of Breast Cancer.”

The need for safe, effective birth control is shared by many women around the world. About 140 million women worldwide use hormonal contraception. Besides effectively stopping unwanted pregnancies, birth control pills also help control other conditions, such as acne, PMS, heavy periods, and mood swings. Research also has shown that birth control pills can slightly lower the risk of uterine and ovarian cancer. There is also some evidence that birth control pills may reduce the risk of colorectal cancer.

Still, research suggested that older forms of hormonal birth control that contained higher doses of hormones were linked to a higher risk of breast cancer. Newer forms of contraceptives that contained lower doses of hormones were considered safer, though all contained warnings in the instructions that they could increase cancer risk. The Danish study reviewed here wanted to quantify that risk.

It’s extremely important to know that if you have been diagnosed with breast cancer, you SHOULD NOT use contraceptives that use hormones. There is evidence that hormonal contraceptives may increase the risk of the cancer coming back (recurrence).

To do the study, the researchers looked at the medical records of all women living in Denmark between the ages of 15 and 49 as of Jan. 1, 1995. They excluded women who:

  • had been diagnosed with cancer
  • had been diagnosed with a blood clot
  • had been treated for infertility

A total of 1,797,932 women were included in the study. The women were followed for an average of about 11 years.

Because Denmark has national healthcare, the researchers were able to look up information on how many women used hormonal birth control and which type they used. They also looked up how many of the women were diagnosed with invasive breast cancer.

During follow-up, 11,517 cases of breast cancer were diagnosed among the women.

The researchers found that women who used hormonal contraceptives had a slightly higher risk of breast cancer than women who had never used hormonal contraceptives. They also found that women who used hormonal contraceptives for more than 10 years had a slightly higher risk than women who used hormonal contraceptives for less than 1 year.

To put it in perspective, overall, the increase was about one new breast cancer case per 7,690 women who used hormonal contraceptives for a year. That’s a very small risk.

The risk was also different for women of different ages. For women younger than 35, there was only one additional breast cancer case for every 50,000 women who used hormonal contraceptives for a year.

Additionally, a British study that started in 1968, when levels of hormones in birth control were higher, looked at more than 46,000 women and followed them for up to 44 years. The study found that although there were increases in breast and cervical cancers among women using hormonal birth control, there was no effect on overall cancer rates because the rates of other cancers were reduced. Other studies have shown the same results.

“The risk of breast cancer needs to be balanced against the benefits of the use of oral contraceptives,” wrote David Hunter, professor of epidemiology and medicine at the University of Oxford, in an editorial in the New England Journal of Medicine that accompanied the study. “Beyond the fact that they provide an effective means of contraception and may benefit women with dysmenorrhea or menorrhagia, the use of oral contraceptives is associated with substantial reductions in the risks of ovarian, endometrial, and colorectal cancer later in life. Indeed, some calculations have suggested that the net effect of the use of oral contraceptive for 5 years or longer is a slight reduction in the total risk of cancer.”

In an interview in the New York Times, Dr. Hal Lawrence, chief executive officer of the American Congress of Obstetricians and Gynecologists and an obstetrician-gynecologist himself, said his biggest concern was that the study would “scare women away from effective contraception,” causing unwanted pregnancies. “We’re never going to eliminate all the potential risks that come with medication,” he said. “But we know a lot of the benefits, and the no. 1 benefit is preventing unintended pregnancies and the health and socioeconomic risks that go along with that.”

It’s also important to know that the authors said their study was limited because they could not account for other factors that affect breast cancer risk, such as how much exercise the women got, whether they breastfed or not, whether the women were overweight, and how much alcohol they drank. Since these factors weren’t taken into account, it’s impossible to know how much they influenced the results.

While most gynecologists don’t think that women younger than 40 need to worry about the results of this study, if you’ve been diagnosed with breast cancer or have a higher-than-average risk of breast cancer because of family history or a genetic mutation linked to a higher risk of breast cancer, such as a BRCA1 or BRCA2 mutation, you may be wondering about alternatives to hormonal birth control.

“Easy, effective, and safe alternatives to hormonal contraceptives do exist,” said Dr. Marisa Weiss, founder and chief medical officer of Breastcancer.org. “You have choices.”

Here are some options to consider:

  • barrier methods, including condoms or a diaphragm and spermicide
  • a non-hormonal IUD, such as ParaGard, which is made of copper
  • if you’re absolutely certain you don’t want to have children now or in the future, permanent birth control via surgery for both women and men can be considered; for women, surgery closes the fallopian tubes and stops the eggs from entering the uterus; for men, vasectomy severs and seals the tubes that carry sperm so there is no longer any sperm in the semen

“No matter which type of birth control you decide to use, ask your doctor if you have any questions on how to use it effectively,” Dr. Weiss added. “Birth control is an important choice. It’s better to be safe than sorry and you do have options.”

For more information on birth control and breast cancer risk, read Dr. Weiss’s “Alternatives to the Pill” Think Pink, Live Green column.


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