Women who use birth control pills are less likely to develop ovarian cancer later in life, a new meta-analysis suggests.
Researchers pooled data from 24 studies and found that users of oral contraceptives (OC) had a 27% lower risk of ovarian cancer – and longer use seemed to be tied to more protection.
“It reinforces that there is a positive relationship between the use of oral contraceptives and ovarian cancer prevention in the general public,” said Dr. Laura Havrilesky, who led the study at the Duke University School of Medicine in Durham, North Carolina. “I think it adds some scientific weight to that relationship.”
However, the review can’t prove that using OC use lowers a woman’s risk of disease, because there could have been other, unmeasured differences between women who took the Pill and those who didn’t, researchers noted.
Dr. Havrilesky and her colleagues combined data from 24 studies that compared thousands of women who used birth control pills for various lengths of time, at a range of ages, with those who didn’t use oral contraception.
Any OC use o was linked to a lower risk of ovarian cancer, they found. Women who were on birth control pills for 10 years or longer were half as likely to develop the disease as those who didn’t use them at all, the study team reported Wednesday in Obstetrics & Gynecology.
If OC use was responsible for that reduced risk, the researchers calculated that 185 women would have to use the pills for five years to prevent one case of ovarian cancer.
But because none of the studies were randomized, it’s not clear that the contraceptives themselves account for the whole cancer difference.
The researchers said there hasn’t been enough time to study how the specific hormone formulations in contemporary birth control pills affect ovarian cancer risk decades down the line.
Because of that and other limitations, women should use “considerable caution” when figuring the new findings into their own personal decisions about birth control pills, they wrote.
What’s more, other research suggests OC users are at a higher risk of cervical cancer, said Eduardo Franco, head of cancer epidemiology at McGill University in Montreal, Canada.
“It is the sort of thing that requires a frank conversation between a woman and healthcare provider,” Franco, who wasn’t involved in the new research, told Reuters Health.
He said the findings are not surprising and that many doctors are convinced birth control pills do lower ovarian cancer risk.
“I don’t think there’s a question of the link,” Franco said. What’s important, he added, is “understanding the caveats that come with the reduced risk of ovarian cancer.”
“What we’ve got right now may be the best evidence that we ever are able to have. I don’t necessarily think that it is enough to tell a physician to have their patients use oral contraceptives solely for the purpose of preventing ovarian cancer,” Dr. Havrilesky told Reuters Health.
“But I think it’s enough to say this is a possible advantage in women who are considering use of oral contraceptives” for birth control or other medical reasons, she said.
Obstet Gynecol 2013.
— Genevra Pittman0