A BLESSING AND A CURSE
By Meredith Knight
Wednesday, June 11, 2008.
Birth control pills decrease the risk of certain cancers but increase the risk of others the longer they’re taken, according to the longest study ever done on the hormonal contraceptive. For long-term users, the benefits of the pill are still seen in diminished ovarian and endometrial cancers; but women who took the pill for more than eight years were twice as likely to get cervical cancer.
The study, published in the British Medical Journal, comes 50 years after the pill first gained international approval to help regulate the periods of women with menstrual disorders. Since then, it has also helped more than 300 million women worldwide avoid pregnancy by blocking ovulation.
Because of controversy surrounding its use, researchers kept meticulous data about the women who first took it and the conditions they developed. Now the data have been analyzed, and findings indicate that the pill offers protective benefits for women who’ve used it: a reduction of cancer incidence between 3 percent and 12 percent. But long-term pill takers were 20 percent more likely to develop cancer.
The way birth control protects or damages a woman’s body is not known. One hypothesis suggests that by stopping ovulation, the pill protects the ovaries from the monthly damage caused by an egg breaking through the ovary during a woman’s natural menstrual cycle, thus preventing ovarian cancers.
Another theory is that the hormone regulation induced by taking the pill protects organs, possibly through changes in the production of other non-sex hormones or the body’s ability to process sugar from foods, although both causes are purely speculative.
“None of the mechanisms actually fit all the data, so we just have to say no one knows its precise beneficial or harmful effects,” says Dr. Philip Hannaford, a professor of General Practice and Primary Care at the University of Aberdeen, Scotland, and the lead author on the study.
Hannaford’s team analyzed data from more than 1 million British women who began taking the pill just after it was commercially introduced in 1968. “This study is good news for women,” Hannaford says, mentioning that for many women who worry about increased risk of breast cancer—previously linked to hormone therapies—the findings came as a relief.
However, increased cancer among long-term users was primarily cervical cancer, which was not aggressively screened for until 1975. “Cervical cancer can be picked up early and is eminently treatable,” says Hannaford. He recommends that women using the pill for a long time recognize they have an increased risk and remember to go in for their annual screenings.
Dr. Miriam Cremmer, a family planning specialist at New York University Medical Center, agrees that long-term pill users should not be too concerned. “I wouldn’t tell women to get off it at any point because of increased risk of cancer,” she says.
Cremmer noted that she and her colleagues were not concerned because the risk increase was relatively small and only found for easily identified cancer types. “I don’t think it’s going to change prescriptions at all,” she says.
Meredith Knight is with New York University's Scienceline.
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