Early detection of ovarian cancer remains elusive but, in the meantime, women can significantly reduce their risk of this feared malignancy by using birth control pills and having babies.
Women who take the pill for 10 years nearly halve their risk of developing ovarian cancer, according to a large study that followed about 300,000 European women for an average of nine years.
The study, published this week in the British Journal of Cancer, confirmed findings of previous studies, including a large review in 2008, which reported that so-called "ever use" of the pill is protective. Authors of the latest study said ever-users of oral contraceptives had a 15 percent lower risk of ovarian cancer than never-users, but women who took the pill for a decade or more slashed their risk 45 percent.
Put another way, the researchers found about 15 ovarian cancer cases for every 100,000 women who took the pill for at least a decade, compared with about 28 ovarian cancer cases for every 100,000 women on the pill a year or less.
Women need to individualize their decisions based upon their family history and other risk factors. The pill's protective effect on the ovaries could be particularly important to women with ovarian cancer in their family, but they might want to weigh the protection against increased breast cancer risk associated with hormonal contraceptives. But the breast cancer risk "disappears after use has stopped," according to a statement from Cancer Research UK, which co-sponsored the new study.
"The data on breast cancer and oral contraceptives is still conflicting," Dr. James Speyer, medical director of the NYU Langone Clinical Cancer Center, said Wednesday. "For most women, it does not pose significant risk. For those with strong family histories, they may wish to consider possible increased risk."
With a growing amount of genetic information becoming available, Speyer said, "we may be better able to determine which women gain a greater protective effect from oral contraceptives and which do not. Coupled with other risk factors and family history, we will be better able to advise patients in the future."
Given that the study subjects were European, Speyer said he'd be interested to know "if this applies to other ethnic groups to the same degree, e.g., African and Asian women."
"Ovarian cancer is difficult to detect and so prevention is key to saving women suffering from this disease," said study co-author Naomi Allen, a Cancer Research UK epidemiologist at the University of Oxford. "These results are important because most women don't know that taking the pill or getting pregnant can help reduce their risk of ovarian cancer later in life."
This year, nearly 22,000 U.S. women will be diagnosed with ovarian cancer and 15,460 women will die from it, according to the National Cancer Institute. Among women whose ovarian cancer is detected before it spreads beyond the ovary, 93 percent are still alive after five years, the American Cancer Society says. But the disease is more often detected in advanced stages, when survival rates are far lower.
Recent studies have found that bloating, pelvic or abdominal pain, feeling full quickly when eating and urinary frequency or urgency that persist a couple of weeks or more can be early warning signs and merit medical evaluation.
The 47-member research team, led by cancer epidemiologist Kostas K. Tsilidis, also from Oxford, analyzed the influence of contraceptive use and other reproductive factors on ovarian cancer among 327,396 participants in the European Prospective Investigation into Cancer and Nutrition (EPIC). Among study participants, 59 percent reported ever having taken contraceptive pills. Half of them took the pill for less than 5 years. During an average of nine years' follow-up, 878 of the women developed ovarian cancer.
After pill use, the next most powerful risk reducer was a pregnancy leading to the birth of a first child, which cut risk by 29 percent, compared with never being pregnant. Subsequent full-term pregnancies reduced the risk an additional 8 percent.
Sara Hiom, director of health information for Cancer Research UK, said that given that many women today have smaller families or no children at all, they can do other things to lower their risks "like stopping smoking and maintaining a healthy weight."
Women who reached menopause after age 52 had a 46 percent higher risk of ovarian cancer than women whose childbearing years ended by 45. For every extra year a woman was still menstruating, her risk rose 2 percent.
Although no one knows exactly why oral contraceptives and pregnancy protect the ovaries, they know both reduce the number of times that a woman's reproductive hormones stimulate monthly ovulation and menstruation. Less exposure to that hormonal flux might lower the risk of ovarian cancer. Women who reach menopause later in their lives may have a greater ovarian cancer risk because of prolonged exposure to hormonal fluctuations.
The study found that breastfeeding, the age at which a woman begins menstruating and the age at which she first becomes pregnant had no effect on ovarian cancer risk.
Hiom of Cancer Research UK noted that the risk of ovarian cancer increases as women grow older. "Most cases are in women who are past their menopause," she said.
Ovarian cancer spreads quickly and is particularly deadly in older women, according to two presentations Wednesday at the American Association for Cancer Research Frontiers in Cancer Prevention Research conference in Boston. In both studies, women's use of oral contraceptives reduced the risk of fatal ovarian cancer, MedPage Today reported.