Even low-dose contraceptives may slightly increase risk of breast cancer
The longer women had used hormonal contraception, the greater their risk, study finds
Adapted from a story by The Washington Post’s Linda Searing.
The association between birth control pills and breast cancer was identified years ago. However, many women and their doctors have assumed that newer, lower-dose pills — and other hormonal delivery methods beyond the pill — were much safer.
A new study published in the Dec. 7 issue of the New England Journal of Medicine questions that notion.
The study
The researchers analyzed data on 1,797,932 women younger than 50. None had cancer, and they had not undergone fertility treatment. About 60 percent of the women used some type of hormonal contraception, and about 40 percent did not.
In about an 11-year span, 11,517 women got a breast cancer diagnosis. Researchers concluded:
- Those using hormonal contraception of any sort were 20 percent more likely to have developed breast cancer than were women who did not use it.
- The longer women had used hormonal contraception, the greater their risk.
Who may be affected?
Women who use hormonal contraception. This includes:
- Patches
- Implants
- Injections
- Vaginal rings
- Intrauterine devices
- Birth control pills
In the United States, about 10 million women use oral contraceptives, and more than 4 million others use IUDs or implants.
Caveats
Despite the finding of increased risk, breast cancer is fairly rare among younger women. The study estimated that:
- For every 100,000 women, hormone contraceptive use causes an additional 13 breast cancer cases a year overall.
- There were only 2 cases for every 100,000 women younger than 35.
The risk analysis did not take into account some factors — such as physical activity, alcohol consumption and breast-feeding history — that can affect the risk for breast cancer.
The study also did not include women 50 or older, who are the most likely to develop breast cancer. The study was funded by the Novo Nordisk Foundation.
