Birth Control Pill Tied to Slight Rise in Breast Cancer Risk

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But according to a new study, even the contraceptives with lower dosages of estrogen still come with a slightly increased chance of breast cancer.

What really surprised the researchers was that the increased risk was not confined to women using oral contraceptive pills, but also was seen in women using implanted intrauterine devices, or IUDs, that contain the hormone progestin. But they stress there is no need for most women to abandon birth control pills for fear of breast cancer.

What those numbers mean in terms of actual women getting breast cancer who otherwise may not have is a bit less striking: there was about one extra breast cancer case diagnosed for every 7690 women who used hormonal contraception for a year.

The overall increase in breast cancer risk was relatively small, about 20 per cent higher among current and recent users of oral contraceptives than among those who never used the drugs. That's a lot of cancers, given that 140 million use hormonal contraception worldwide - or about 13 percent of women ages 15 to 49.

Overall, the use of any hormone-based contraceptive for five years or more raised a woman's risk of breast cancer by 20 percent, Lina Morch of the University of Copenhagen and colleagues reported in the New England Journal of Medicine.


The researchers found a similarly increased breast cancer risk in birth control pills that only contain progestin, as well as in IUDs that release progestin.

Dr Chris Zahn, ACOG's vice president for practice activities, acknowledged a link between breast cancer risk and hormone use, but urged concerned women to consult a trusted medical provider before making changes.

Older contraceptives were known to carry a higher risk of breast cancer, but doctors had hoped that the newer lower-estrogen formulations might pose a lower risk.

Mørch said that "knowledge is needed on the potential beneficial influence of newer contraceptives on the risk of ovarian and colorectal cancer, since evidence now relates to older types of hormonal contraceptives".

"Unfortunately this was not the case and additional research is needed to tweak the formulation".


Despite the risk, women will continue to use the pharmaceuticals, Morch said. "Depending on their reasons for using oral contraceptives, they might want to consider other options, including non-hormonal contraceptives". But he suggested doctors take time to discuss the pros and cons of different types of contraception with their patients, and that they be frank about the potential risks, suggesting women reassess hormone use as they age.

A hormone specialist at Brigham and Women's Hospital who deals with contraceptive issues says the study shouldn't alarm those taking oral contraceptives. "But in the study it does appear that any form is basically the same", added Dr. Taraneh Shirazian of New York University's Langone Joan H. Tisch Center for Women's Health.

Many studies show that oral contraceptives can also reduce the risk for cancer of the ovaries, uterus and possibly the colon.

Mørch explained to MedPage Today that "there was a lack of evidence on contemporary hormonal contraception and risk of breast cancer". Over the years, makers of birth control pills and hormone replacement therapy for women past menopause have reduced the amount of estrogen in their products. According to an editorial that accompanied the study in NEJM, birth control may actually be protective against cancer on the whole despite this increased risk for one type.

The increase in breast cancer cases associated with hormones was also small because young women are at low risk to begin with.


"The relative risk increase in this study is only 1.2 on average". "The range of risks we're talking about here is much much smaller", she said.

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