The slight increase in breast cancer risk from hormonal contraceptives has been documented for decades—and it’s not just the pill

Birth Control and Breast Cancer: Progestin-Only Methods Carry Similar Risk to Combination Options

The slight increase in breast cancer risk from hormonal contraceptives has been documented for decades—and it’s not just the pill

• New research found that progestin-only birth control provides the same risk of breast cancer as combination birth control containing estrogen.
• Researchers note that this risk is still very small, and should be one of many factors considered when choosing a birth control option.
• Experts recommend patients gather a well-rounded picture of birth control benefits and risks before making a decision.

A recent study from the U.K. found that progestin-only methods of birth control carry about the same risk of breast cancer as options containing estrogen.

“Many more women over the last 20 to 30 years have been using progesterone-only contraceptives,” said Stephanie Teal, MD, MPH, an obstetrician and gynecologist-in-chief at University Hospitals Health System in Cleveland, Ohio, who was not involved with the new research.

Dr. Teal cited one reason for this is estrogen can cause blood clots. Progesterone-only birth control—sometimes called progestin-only—also stops or drastically reduces monthly bleeding, which some people prefer over having a monthly period.

Starting in the 1990s, research has shown that contraceptives that contain a combination of the hormones estrogen and progesterone slightly increase the risk of breast cancer. 

“But we didn’t know if you used just progesterone without the estrogen in it, does that carry the same risk?” Dr. Teal explained.

Progestin-only options include birth control pills (the so-called mini pill), implants, intrauterine devices (IUDs), and injections. Nearly 15% of women in the U.S. ages 15 to 49 use oral contraceptive pills. Just over 10% use long-acting reversible methods such as IUDs or implants, Centers for Disease Control and Prevention (CDC) data show.

According to Gill Reeves, PhD, director of the Cancer Epidemiology Unit at the University of Oxford in England, who co-authored the new study, the risk of breast cancer hormonal contraceptives is still small, and should not be the only factor a person considers when choosing a form of birth control.

“We are not suggesting that women necessarily need to alter their method of contraception because of this study,” she told Health. “This effect is small and declines after women stop taking them, and should be viewed in the context of the many established benefits of taking hormonal contraceptives during the reproductive years.”

Progestin-Only Birth Control and Breast Cancer Risks

In order to assess progestin-only birth control’s breast cancer risk, Dr. Reeves and her team analyzed medical records from nearly 9,500 women who were diagnosed with breast cancer between 1996 and 2017. These patients were compared to about 18,000 who had not been diagnosed with breast cancer during that time frame. All medical records were pulled from the Clinical Practice Research Datalink, a U.K. primary care database.

About 44% of the women who had breast cancer—4,195 total—and 39% of the controls who had not been diagnosed with breast cancer—7,092—were on some type of hormonal contraceptives for an average of about 3 years before their breast cancer diagnosis. About half were progestin-only methods.

They found that progestin-only methods raised breast cancer risk by about the same amount as combined estrogen and progesterone contraceptives—but that increased risk was still small.

According to the National Cancer Institute, a woman’s lifetime risk of developing breast cancer is about 13%, though the chances of getting a breast cancer diagnosis during reproductive years are much lower.

Most breast cancer happens when people are in their 70s and 80s, a group that does not typically use hormonal contraceptives, noted Dr. Teal. Breast cancer risk remains slightly elevated while a person is using hormonal contraceptives and goes back to baseline within about 10 years after they stop using it, she added.

According to Dr. Reeves: “The number of extra breast cases associated with hormonal contraceptive use will vary depending on the age at which women use them because the underlying risk of breast cancer increases with age.”

Dr. Reeves and her team found that the increased risk of breast cancer a woman sustains up to 15 years after starting to use progestin-only contraceptives is about 0.01% for those who started using them between the ages of 16 to 20, which means the chance of developing breast cancer goes from 0.08% to 0.09%. That jump increases to around 0.2% when people use them in their late 30s, which translates to going from a 2% chance to a 2.2% chance of developing breast cancer.

“When we’re talking about birth control to someone in their early 20s, this is so negligible,” Dr. Teal explained, noting that it’s still an important risk to understand since so many women are exposed to hormonal birth control at some point in their lives. 

“Although there are a lot of good reasons why people might choose a progesterone-only method, this study shows that a slight increase in the risk of getting a breast cancer diagnosis is not solved by using a progesterone-only method,” she emphasized.

Birth Control Methods Are a Personal Choice

Both Dr. Teal and Dr. Reeves stressed that contraception is a deeply personal choice that people should make with their doctors, and it is based on many different factors.

“Non-hormonal forms of birth control such as barrier methods are unlikely to affect breast cancer risk, but they will not necessarily be as reliable as hormonal contraceptives,” Reeves said. “Any woman who is considering changing her form of birth control should discuss this with an appropriate health professional.”

Long-lasting non-hormonal birth control methods, such as the copper IUD, also do not appear to raise breast cancer risk, though no method comes without its own risks. And while many studies have shown that hormonal birth control slightly increases the risk of breast cancer, it has also been shown to reduce the risk of other cancers, including endometrial, uterine, and ovarian cancer, according to the National Cancer Institute.

Pregnancy prevention and the treatment of conditions such as endometriosis or ovarian cysts are also important factors one may need to consider when choosing a contraceptive.

“When people are looking at the pros and cons of different contraceptive methods, it’s important not to cherry-pick one finding that you heard about contraception,” Dr. Teal encouraged. “You have to put it in the full context.”

This story originally appeared on: Health News - Author:Kaitlin Sullivan