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Study links breast cancer to high-dose estrogen birth control pills

CTCA

blog breast cancer birth control

You may have heard that taking the birth control pill increases your risk of cancer, but does it matter which pill you take? A team of researchers analyzed different pill types and found a 50 percent increase in breast cancer risk among women taking high-dose estrogen pills.

The good news is that low-dose pills did not seem to increase breast cancer risk, according to the recent study in Cancer Research. Today, most women on birth control pills use the low-dose kind. In fact, only 1 percent of the women in the study were taking high-dose pills between 2005 and 2009.

Previous studies have shown that oral contraceptives may slightly increase in the risk of breast, cervical and liver cancers, while slightly decreasing risk of uterine and ovarian cancers. Those studies, though, relied on self-reported use of the pill and did not evaluate how the pill’s estrogen dosage may affect cancer risk.

The new study looked at pharmacy records to determine which oral contraceptives the 1,102 women in the study were taking. Researchers identified three types of pills by dosage:

  • Low-dose estrogen pills of about 20 micrograms of ethinyl estradiol (such as Loestrin 1/20®, Mircette®, Yaz® and Lybrel®)
  • Moderate-dose pills of 30-35 micrograms of ethinyl estradiol or 50 micrograms of mestranol (such as Loestrin Fe 1.5/30®, Lo/Ovral®, FemCon Fe®, Norinyl 1+35® and Ovcon 35®)
  • High-dose pills of 50 micrograms of ethinyl estradiol or 80 micrograms of mestranol (such as Ovcon 50®, Zovia 1/50®, Norinyl 1+50® and Ogestrel 0.5/50®)

The researchers compared women who developed breast cancer to a control group of 21,952 women who did not have breast cancer, and were either never on the pill or stopped taking it before the study.

The women taking high-dose pills were 2.7 times more likely to have breast cancer and those on moderate-dose pills were 1.6 times more likely. Women using low-dose pills had no increased risk.

The study noted that Sprintec® 28, the most-prescribed pill in 2013, increased breast cancer risk by 20 percent. Loestrin 24 Fe®, the fifth-most prescribed pill last year, raised risk by 60 percent.

Dr. Justin Chura, Medical Director of Gynecologic Oncology at our hospital in Philadelphia, says the study’s results should be interpreted with caution. “The authors are very quick to point out that the results are preliminary,” he says.

While the pill’s link to breast cancer may cause concern, Dr. Chura points to the well-established benefits of birth control pills:

  • Family planning
  • Regulating menstrual cycles
  • Decreasing menstrual symptoms, such as pain
  • Treating endometriosis
  • Preventing ovarian cysts
  • Reducing the risk of ovarian and uterine cancers

“One would not advocate that women stop using the birth control pill based upon the results of the study,” Dr. Chura says. “Instead, we advocate for discussion between patient and physician so that informed decisions are made.”

About one in eight women will be diagnosed with invasive breast cancer during her life. Age is the predominant risk factor, as a woman’s risk increases as she gets older.

Learn more about risk factors for breast cancer.

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