Newer Birth Control Pills Also Protect Against Ovarian Cancer
WebMD News Archive
July 24, 2000 -- Although today's birth control pill contains smaller amounts of the hormones estrogen and progestin than earlier versions of the pill, it protects women against ovarian cancer just as well, a new study shows.
Doctors have long known that taking birth control pills for just a few years can significantly reduce a woman's risk of getting ovarian cancer. Many, though, had believed that the new lower-dose pills might not protect at the same level. But the study, published in the American Journal of Epidemiology, says the newer pills provides as much ovarian cancer protection as the older ones did.
The study of more than 2,000 women found that the low-dose pill, introduced around 1980, cuts the risk of ovarian cancer by about 40%. Earlier studies have shown that use of the older, higher-dose pill reduces the risk of ovarian cancer in women in the general population, as well as those who are at high risk due to a genetic predisposition. Levels of estrogen and progestin in the pill were lowered because of fears that high doses might pose a risk of heart disease, stroke, and other serious health problems.
"You have to be on it for a minimum of somewhere around one to four years [to get the benefits]," explains the study's author, Roberta Ness, MD, PhD, of the University of Pittsburgh. According to her study, the protection against ovarian cancer is seen no matter at what age a woman begins taking the pills, and continues for 30 years or more after she stops taking them.
"Once you've been taking it for a year, you get some protection," Ness tells WebMD. "Once you've been taking it for four or five years, you get as much protection as someone who has been taking it for an even longer time."
Ness says there are two theories for how the pill protects against getting the cancer.
The first is that the contraceptive lowers levels of a hormone that regulates the ovaries. Some researchers believe that at high levels, this hormone can be destructive enough to trigger ovarian cancer.
The other theory is that ovarian cancer is related to inflammation in the ovaries. "Every time you ovulate, you create a wound. When you close that wound, you have an inflammatory process, so, in fact, with each ovulation there is a bout of inflammation," Ness says. By preventing ovulation, the pill also prevents the inflammation that ovulation would cause.
Laboratory and animal studies will be needed to test this theory, but Ness says she's a believer. She says her study and others like it are making researchers rethink the causes behind ovarian cancer.
Women with a family history of ovarian cancer are much more likely than those with no such history to develop the disease. Ness says such women definitely should take the pill as a precaution. Another option for women at very high risk of this type of cancer is removal of the ovaries -- but this can double or even triple the risk for heart disease, bone thinning, and other conditions related to the loss of estrogen.