Published: Thu, December 07, 2017
Health | By Jay Jacobs

Some birth control raises risk of breast cancer, study says

Some birth control raises risk of breast cancer, study says

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.

Women who now use or recently used hormone-based contraception face a 20 percent higher risk of breast cancer, although the overall risk for most women is relatively low, a new study of 1.8 million women in Denmark has concluded. "Indeed, some calculations have suggested that the net effect of the use of oral contraceptives for 5 years or longer is a slight reduction in the total risk of cancer", Hunter said.

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.

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.

The study of nearly 2 million women in Denmark looked at women using birth control methods such as the pill, NuvaRing, or implants.

"Another thing that has not been clear before is that after discontinuation, if you have used this product for more than 5 years, the risk seems to be increased, even after 5 years of discontinuation of the drugs", chief author Dr. Lina Morch, a senior researcher at Copenhagen University Hospital told Reuters Health by phone. The link with cancer risk exists not only for older generations of hormonal contraceptives but also for the products that many women use today, according to a paper published Wednesday in the New England Journal of Medicine. Out of those women, for every 100,000 participants, the use of hormonal birth control caused an additional 13 cases of breast cancer each year.

Still, experts cautioned that the absolute risk of breast cancer for any one woman on the Pill remains very low. "But it does show an increased risk, so for people who don't have a great reason for taking oral contraceptives, or are amenable to alternatives, perhaps they should think about it". The women were followed for almost 11 years.

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

"I don't think anyone's going to say stop taking oral contraceptives".

There was optimism that newer, low-dose contraceptives would lower the breast cancer risk, but these results have dashed those hopes, said Gaudet, who wasn't involved in the research.

Despite the risk, women will continue to use the pharmaceuticals, Morch said.

Digging further, the researchers found no differences among types of birth control pills.

They include smoking, obesity, starting menstruation early, having children late in life or not at all and not breastfeeding.

"And there is also the reassuring thought that oral contraceptive use may decrease the risk of ovarian and endometrial cancer". The findings indicate that the hormone progestin is adding to breast cancer risk; some of the contraceptive pills and numerous IUDs included only progestin, Mørch said.

"Estrogen has been the primary focus of breast cancer research in general, and so we know much more about it than we do progesterone", Gaudet said. Don't forget there is relative risk of death in pregnancy, too.

Mørch explained to MedPage Today that "there was a lack of evidence on contemporary hormonal contraception and risk of breast cancer". A 20 per cent increase raises her risk to 1.74 per cent, or 1 in 57.

Duration of use also contributed to associated breast cancer risk.

In Denmark, older women who have completed their families are most likely to use IUDs, including those containing hormones, and they are already more likely to develop breast cancer because of their age, Mørch said.

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