Study Finds Glitch in The Pill's Cancer Protection
Effect of gene mutation on ovarian cancer debated
WEDNESDAY, July 25, 2001 (HealthDayNews) -- Contradicting earlier studies, an Israeli-American research team reports birth control pills don't reduce the risk of ovarian cancer in women who carry a genetic mutation that makes them vulnerable to the malignancy.
"It is quite well-established that women who use oral contraceptives have a lower risk of ovarian cancer," says Sholom Wacholder, a senior investigator at the National Cancer Institute and a member of the research team. "But in our study, we found that women who are at highest risk because they carry one of the alterations of the BRCA1 or BRCA2 gene show no evidence of protection."
The study, which appears in tomorrow's New England Journal of Medicine, did find use of birth control pills reduced the incidence of ovarian cancer in women who don't carry the mutations. It also found that having children reduced the risk for women, whether they carried the mutation or not.
The reason for the difference in protection is not clear, Wacholder says.
"We're trying to understand what's going on," he says.
The findings should be approached with great caution, says Dr. Richard Barakat, associate chief of gynecology at Memorial Sloan-Kettering Cancer Center in New York. He has researched the subject and cites other studies for his skepticism.
"I don't think this study refutes the stronger findings of studies at the University of Toronto. It has been clearly known for years that oral contraceptive use decreases the risk of ovarian cancer. There is a protective effect of use for as little as one year, and for use of three years, there is up to a 50 percent reduction in risk," he says.
That protection has been shown for high-risk women, including those who carry the genetic mutations, Barakat says. He attributes the Israeli findings to the small number of women in the study.
That study involved 840 women with ovarian cancer, including 244 who had the BRCA1 or BRCA2 mutations, which are known to increase the risk of both breast and ovarian cancer. Overall, the researchers conclude that "each additional birth and each additional year of use of oral contraceptives were found to lower the risk of ovarian cancer, as expected."
But "oral contraceptive use appeared to reduce the risk only in non-carriers," the researchers write.
"With further research, the issue may be clarified," Wacholder says. "We are figuring out what we may be able to do here at the cancer institute and with outside researchers."
Barakat says research at Sloan-Kettering and elsewhere doesn't support a difference in protection for women with the genetic mutations.
"The theory is that ovarian cancer starts on the surface of the ovary. When a woman ovulates, it creates a cyst, and that is where cancer begins. So anything that can inhibit ovulation -- pregnancy, breast-feeding, oral contraceptives -- will reduce the risk of ovarian cancer," he says.
Birth control pills also contain progesterone, which has been shown to reduce ovarian cancer risk, Barakat says.
What To Do
"I don't want people to get the message from this study that oral contraceptives are not protective against ovarian cancer," Barakat says. "I wouldn't want people to stop taking them on the basis of this study. I don't think it disproves the previous studies."