A study published Wednesday has linked newer-generation birth control pills with breast cancer; the link had already been established for older variants of hormonal contraception.
The data for the study was collected from 1.8 million Danish women for more than a decade.
That number might seem small, but when you consider the many millions of women who take the pill, it becomes a lot more significant.
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. They compared what happened over almost 11 years among women taking hormonal birth control and women using other methods.
Hopes that different formulations would remove a longstanding danger to women are dashed by a new study.
The research also suggests that the hormone progestin - widely used in today's birth control methods - may be raising breast cancer risk.
One thing reiterated by every doctor Newsweek spoke to: Women who are anxious about how their contraception might increase their risk of breast cancer should speak with their health care provider.
"Gynecologists just assumed that a lower dose of hormone meant a lower risk of cancer".
The search for new hormonal contraceptives - methods that don't elevate breast cancer risk at all - should continue, Hunter says. The study's published in The New England Journal of Medicine, and NPR's Patti Neighmond has our report. "It's important that women feel confident and comfortable with their contraceptive choice", he said. "Why not pursue another option?" "So, many calculations suggest that the use of oral contraceptives actually prevents more cancers than it causes".
PATTI NEIGHMOND, BYLINE: Scientists have long known contraceptives that contain estrogen can increase the risk of breast cancer. Yet the new study found increased risks that were similar in magnitude to the heightened risks reported in earlier studies based on birth control pills used in the 1980s and earlier, Hunter said. The hope was the lower dose would decrease breast cancer risk. "It is a very clear picture for us, very convincing". During that time period, 11,517 cases of breast cancer were identified. Relative to the increased risk posed by other environmental factors, like smoking for lung cancer-that's about a 10 times greater risk-and having a human papillomavirus infection for cervical cancer-that may increase risk about 50 or 60 times-38 percent really isn't that much. Still, the additional risk would result in a comparatively few additional cases of breast cancer, the researchers said. And there's a strong suggestion they also reduce the risk of colorectal cancer. But the odds rose among women who used hormonal contraception for more than 10 years, the study found.
Researchers in Denmark analyzed data on 1.8 million women and found that using any type of hormonal contraceptive was linked to a 20-percent higher risk of breast cancer.
NEIGHMOND: All of these forms of hormonal contraception increased breast cancer risk by 20 percent. It's even lower among younger women since breast cancer in this age group is relatively rare.
NEIGHMOND: Now, it's important to note in the study, women over 40 were more likely to suffer breast cancer than younger women in their 20s and 30s.
"It's a 20 percent increase in risk, but the absolute risk is very low", Dr. Joann Manson said. By contrast, there was no increased risk for breast cancer seen in women who used hormones for less than one year.