Even low-dose birth control pills can raise breast cancer risk

Even low-dose birth control pills can raise breast cancer risk

A new study is showing the link between the use of birth control to increased risk of breast cancer. After all, it means that almost a quarter of American women are doing something that might increase their risk of developing breast cancer by a third-in theory. "It's important that women feel confident and comfortable with their contraceptive choice", he said.

The prospective study included a cohort of 1,797,932 women from Denmark ages 15-49, participating in The Danish Sex Hormone Register Study.

Even newer lower-dose birth control pills raise a woman's risk of breast cancer, although the actual danger is "quite small", researchers reported Wednesday. Women who used any form hormonal contraception for more than 10 years (1.38, 95% CI 1.26-1.51) had a higher risk compared to those who reported less than 1 year of use (1.09, 95% CI 0.96-1.23)(P=0.002), they wrote online in the New England Journal of Medicine. Most cases of breast cancer were seen in women using oral contraceptives in their 40s.

On the other hand, among women who used hormonal contraceptives for short periods, the excess risk of breast cancer disappeared rapidly after use was stopped, the researchers said.

The first wave of birth control pills contained doses as high as 150 micrograms of estrogen. And for those who take the drugs for five years or more, the risk will persist for as long as five years after they stop, she said.

"It's a 20 percent increase in risk, but the absolute risk is very low", Dr. Joann Manson said.

Overall, the study found that women who used birth control had a 20 percent increase in their relative risk for developing breast cancer.

The idea that there is a link between hormonal contraceptive use and breast cancer is not new.

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Two types of birth control pills are sold in the USA - one that combines synthetic versions of the hormones estrogen and progesterone, and the "minipill" that only delivers progestin, a synthetic formulation of progesterone.

Beyond the fact that they provide an effective means of contraception and may benefit women with menstrual cramping or abnormal menstrual bleeding, "the use of oral contraceptives is associated with substantial reductions in the risks of ovarian, endometrial, and colorectal cancers later in life". "Taking a very low absolute risk and increasing it only slightly is still a relatively low risk".

"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. 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.

First, the study didn't factor in other variables like diet, physical activity, breastfeeding or alcohol consumption, which could also have an impact on developing breast cancer. 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".

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.

Women who stayed on hormones for 10 or more years experienced a 38 per cent increase in their relative risk of developing breast cancer, compared with nonusers.

"No type of hormone contraceptive is risk-free unfortunately", said lead author Lina Morch of Copenhagen University Hospital. 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.

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