After a Danish study last week reported finding more breast cancer cases among women who use hormone-based birth control methods, many women were left wondering: How significant is the risk, and what are the alternatives?
The answer will be different for each woman and will depend on such factors as her age and general health and her other risks for breast cancer. But many doctors who prescribe contraceptives say there is no cause for alarm — and no one should throw away her pills and risk an unwanted pregnancy.
The increased breast cancer risk identified among hormone users in the study was small. For the vast majority of women in their 20s and 30s, breast cancer is rare to begin with, so this modest increase would not amount to many additional cases.
A complex link
And while birth control pills may slightly raise the odds of breast cancer — and have been associated with increases in cervical cancer, as well — the contraceptive’s relationship with cancer is complex.
Oral contraceptives appear to reduce the incidence of some less common reproductive cancers, like endometrial cancer and ovarian cancer, which is often detected at an advanced stage, when it is hard to treat. There is some evidence that birth control pills may also reduce the odds of colorectal cancer.
A British study of more than 46,000 women who were recruited in 1968, during the early days of the pill, and followed for up to 44 years found that despite increases in breast and cervical cancers among those who used the pill, the effect on overall cancer rates was neutral, because other cancers were reduced.
Other studies have reached the same conclusion.
“In aggregate, over a woman’s lifetime, contraceptive use might prevent more cancers” than it causes, said David J. Hunter, a professor of epidemiology and medicine at University of Oxford in Britain, who wrote a commentary on the Danish study published in The New England Journal of Medicine last week.
“There is good data to show that five or more years of oral contraceptive use substantially reduces ovarian cancer and endometrial cancer risk, and may reduce colorectal cancer,” he said. “And the protection persists for 10 or 20 years after cessation.”
While the new study’s findings about breast cancer are important, “these results are not a cause for alarm,” said Dr. JoAnn E. Manson, a professor of women’s health at Harvard Medical School and chief of preventive medicine at Brigham and Women’s Hospital. NYT
