A study published last week in the New England Journal of Medicine (NEJM) found a slightly elevated breast cancer risk among women who used low-dose hormonal birth control.
The roughly 20 percent increased risk of breast cancer—similar to the extra breast cancer risk contributed by physical inactivity, excessive weight gain in adulthood, or drinking an average of one or more alcoholic drinks per day—was found to be the same no matter what method of hormonal birth control was used.
When we spoke to Maine Family Planning medical experts, they said women and teens contemplating hormonal birth control (like the Pill, or long-acting reversible contraceptives/LARCs) should not be alarmed by the new research.
For one thing, this was an observational study and therefore it does not prove conclusively that hormonal contraception is definitely the cause of the increased risk—only that it may be a factor, just like female gender or advancing age.
As Aaron Carroll, professor of pediatrics at Indiana University School of Medicine, further explained in Sunday’s New York Times: “This was a prospective cohort study, meaning it was an observational study that followed women over time and saw what happened to them naturally. The data set didn’t allow for adjusting for some factors that could also be associated with breast cancer, like age at first menstruation; whether women breast-fed; whether they consumed alcohol and how much; whether they were physically active; and more. The study found only an association, and not causal proof you might obtain from a randomized controlled trial.”
For another, the increased risk documented by the researchers is still quite small, amounting to one additional case of breast cancer in every 1,500 women. And young women bear even less of the impact.
“The absolute increase in risk [found in the study] is 13 per 100,000 women overall, but only 2 per 100,000 women younger than 35 years of age,” wrote epidemiologist David Hunter, of the University of Oxford, in an editorial accompanying the study in NEJM.
Meanwhile, hormonal contraception continues to carry well documented benefits, including its efficacy in preventing unwanted pregnancy (which carries its own significant health issues), and substantial reductions in ovarian, endometrial, and colorectal cancers later in life. The New York Times spoke with a number of doctors who cautioned against reading too much into the research findings:
While the new study’s findings about breast cancer are important, “these results are not a cause for alarm,” said Dr. JoAnn E. Manson, a professor of women’s health at Harvard Medical School and chief of preventive medicine at Brigham and Women’s Hospital.
“It’s really problematic to look at one outcome in isolation. Hormonal contraception has a complex matrix of benefits and risks, and you need to look at the overall pattern.”
“When it comes to making your own personal health choices, you need to consider the entire set of benefits and risks,” said Kohar Der Simonian, MD, Medical Services Director for Maine Family Planning. “If you have concerns, the best thing to do is to bring them to your doctor or health care provider and find the solution that’s the right fit for you, as an individual.”
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