美国国家公共电台 NPR Even Low-Dose Contraceptives Slightly Increase Breast Cancer Risk（在线收听）

MARY LOUISE KELLY, HOST:

New research finds an increased risk of breast cancer among women who are using hormonal birth control. The study's published in The New England Journal of Medicine, and NPR's Patti Neighmond has our report.

PATTI NEIGHMOND, BYLINE: Scientists have long known contraceptives that contain estrogen can increase the risk of breast cancer. But researchers in Denmark looked at 1.8 million women between the ages of 15 and 49 to see if new lower-dosed formulations are still risky. They compared what happened over nearly 11 years among women taking hormonal birth control and women using other methods. Epidemiologist Lina Morch headed the study.

LINA MORCH: We found approximately a 20 percent increased risk among women who currently use some type of hormonal contraception.

NEIGHMOND: Hormonal contraception releases estrogen, progestin or a combination of both to suppress ovulation and prevent pregnancy. Mia Gaudet with the American Cancer Society says the findings are compelling because researchers didn't just look at the birth control pill. They looked at all birth control methods that release hormones.

MIA GAUDET: Including the patch, the ring, the implant, as well as IUD.

NEIGHMOND: All of these forms of hormonal contraception increased breast cancer risk by 20 percent. And the longer women used this type of birth control, the more breast cancer risk increased. The findings are disappointing, says epidemiologist David Hunter with the University of Oxford. Over the past few decades, researchers tried to develop new hormonal formulas using less estrogen, which is known to promote breast cancer. The hope was the lower dose would decrease breast cancer risk. But that's not what this study found.

DAVID HUNTER: Unfortunately, the increase of 20 percent appears to apply to the most recent formulations just like it did in the '70s, '80s and '90s. So this tells us that things haven't changed.

NEIGHMOND: Lead researcher Morch says the findings should serve as a caution but not an alarm. A 20 percent increase translates into only one extra breast cancer case for nearly every 8,000 women. It's even lower among younger women since breast cancer in this age group is relatively rare.

MORCH: So it has to be balanced - the pros and cons of these contraceptives. And if it's not needed to take hormonal contraceptions, it might be worth considering using other methods like the copper IUD or barium if it's - like condoms, for instance.

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. Age, family history and weight gain later in life all contribute to breast cancer risk. Morch suggests women over 40 discuss possible alternatives with their doctor. And epidemiologist Hunter says there are other clear benefits of hormonal contraception.

HUNTER: There's very good evidence that oral contraceptives reduce the risk of ovarian cancer. They reduce the risk of endometrial cancer. There's a strong suggestion they actually reduce the risk of colorectal cancer. And so many calculations suggest that use of all contraceptives actually prevents more cancers than it causes.

NEIGHMOND: Hunter says the search for new hormonal contraceptives that don't elevate breast cancer risk should continue. Patti Neighmond, NPR News.