Cancer

What Was Found: Of the women with ovarian cancer, 31% had taken the pill at some point in their lives, compared to 37% of the women who did not have ovarian cancer. The longer women used the pill, the lower their ovarian cancer risk. Taking the pill for 15 years or more cut a woman's risk of ovarian cancer by 58%; 10-14 years of pill use cut risk by 44%; and 5-9 years of use cut risk by 36%. But even women who used the pill for only 1-4 years saw a benefit; their risk was cut by 22%.
Although the benefit of the pill got weaker the longer it had been since women took it, the protective effect was still significant even 30 or more years after pill use stopped. The researchers did not see a different level of risk reduction from different estrogen doses in the pill.
"It is reasonable to expect that even current lower dose pills will be as protective as the older versions. However, we do not have definitive evidence to show this and won't for many years," said Saslow.
The study authors estimated that during the past 50 years, 200,000 cases of ovarian cancer and 100,000 deaths worldwide have been prevented by oral contraceptive use, and that if use remains at the current level, as many as 30,000 ovarian cancers could be prevented a year.

The Bottom Line: In an editorial accompanying the study, Eduardo L. Franco and Eliane Duarte-Franco of the Departments of Oncology and Epidemiology at McGill University call this study a "major contribution to our understanding of the role of oral contraceptives in the causation or prevention of ovarian cancer." But they caution that calculating the overall effect on women's health will be tricky.
While birth control pills could reduce a woman's risk of developing ovarian cancer by close to 50%, they could also raise the risk for cancers of the breast and cervix. And though these drugs are generally considered safe, they can also cause side effects like blood clots. Birth control pill use should be evaluated on a case-by-case-basis, they say.
The American Cancer Society does not currently make recommendations about taking oral contraceptives as a prevention measure against ovarian cancer, Saslow said.
And while this report is good news in the fight against ovarian cancer, there's a lot more that needs to be done. Only 20% of ovarian cancers are found at an early stage, and just 45% of women who receive an ovarian cancer diagnosis live past 5 years. More research focused on finding ovarian cancer early and improving treatment is needed, as well as on the best management and care for women who see a doctor because they have symptoms that may be associated with ovarian cancer.
For more information, see our detailed guide, Ovarian Cancer.