Is there a link between the birth-control pill and breast cancer?

What women really think about news, politics, and culture.
Sept. 17 2010 1:00 PM

The Pill-Breast Cancer Connection

Does it exist?

Pill pack of birth control pills. Click image to expand.
A recent study links the pill with a form of breast cancer

Last summer, in a study of more than 50,000 African-American women, Boston University epidemiologist Lynn Rosenberg found a 65 percent increase in a particularly aggressive form of breast cancer among those who had ever taken the birth-control pill. The risk doubles for those who had used the contraceptive within the past five years and had taken it for longer than 10 years.

This unwelcome news doesn't fit well into the wave of coverage of the pill's 50th anniversary. A Newsweek columnist gushed that the pill "did more good for more people than any other invention of the 20th century." In a cover story, Time magazine extolled the pill as "the means by which women untied their aprons, scooped up their ambitions and marched eagerly into the new age." (True. Thanks, pill!) A commemorative MSN.com piece flatly asserted earlier this year that "taking the pill has no impact on breast cancer risk."

Rosenberg's findings question that assertion. She wanted to study black women because they have been underrepresented in cancer research so far, even though they suffer from higher rates of "triple negative" breast cancer. This relatively rare form of breast cancer, in which the tumors lack certain genes and so are not responsive to standard treatments like tamoxifen, confers the highest and fastest mortality. In Rosenberg's work, it was these cancers that were linked to the pill. A number of other studies of women of multiple races support her data implicating the pill in breast cancer, including research done in New England; South Carolina; Long Island, N.Y.; and Scandinavia.     

At the same time, other large studies, including one published in the New England Journalof Medicine in 2002, found no increase in breast-cancer risk among pill users. Further complicating the health-risk equation, it's already well-established that the pill offers some protection to women from ovarian and endometrial cancers. One recent study of 46,000 women over the age of 40 by the Royal College of General Practitioners found that, despite a small increased risk of breast cancer in women under 45, pill-users as a whole actually live longer than other women. But this becomes less surprising when you figure that women who pop the pill tend to be healthier to begin with (for one thing, they have to see a doctor regularly in order to get a prescription).

So what are we to make of the breast-cancer connection? If it exists, why aren't the studies consistent? For one thing, Rosenberg explains that the association she found is relatively small. Compare the 65 percent increase in risk with the 2,000 percent increase in risk of lung cancer linked to smoking. Patterns are hard to spot because even when researchers use a large sample size, only a much smaller number of people will get cancer. (Even the smoking-lung cancer connection took decades of epidemiological head-scratching to figure out.) And if the pill is mostly causing the rare triple-negative type of breast cancer, the effect could be muddied in a study looking at breast-cancer disease overall.

For many women around the world, the benefits of the pill will outweigh the risks. But that doesn't excuse the media and many doctors from underplaying them. Maybe they're just throwing up their hands in the face of competing statistics, but more likely there's some good old-fashioned paternalism at work. "From a doc's point of view, the pill is so easy," says Irwin Goldstein, the director of Sexual Medicine at Alvarado Hospital in San Diego and an outspoken critic of the pill. "You give it to a freshman in college, and you don't have to worry about her getting pregnant. It's good for society, and if there are side effects, too bad."

For younger women in particular, the pill is "safer than it used to be, but it still has some adverse effects," says BU's Rosenberg. In general, she counsels, women of any age who have been on the pill for 10 years or more might want to consider switching to a different form of birth control. Goldstein says he prefers his patients use either nonhormonal contraceptives or low-dose hormonal IUDs such as Mirena, which send their synthetic hormones to a small, localized part of the body.

Every woman's personal comfort zone is different. As it is, a lot of women decide the pill isn't for them, for one reason or another. Globally, half of all women stop taking it within the first year, according to John Townsend, vice president for reproductive health at the Population Council. That organization is actively working to bring new contraceptives to market. Frankly, it's about time. "Women would like safer options with fewer side effects," says Townsend. One new formula (for a vaginal ring) would replace the synthetic estrogen with estradiol, a natural estrogen, which Townsend says reduces risk of blood clots. A new ring is under development using a substance called ulipristal acetate, now available in the new morning-after pill ellaOne. * Unlike the standard contraceptive pill, its synthetic progesterone appears not to bind to breast receptors or cause cell growth.

It might be a breast-cancer-free pill. Then again, it could have other problems. If it's anything like the pill, it will take a good long time to know for sure.

Correction, Sept. 21, 2010: The original sentence called this new contraception a pill rather than a ring. (Return  to the corrected sentence.)

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