The Pill May Reduce Risk of Ovarian Cancer
April 20, 2000 -- Childbirth and oral contraceptives may reduce the risk of ovarian cancer up to the age of 49, according to a report in the March issue of the journal Epidemiology. But researchers say the protective effect of oral contraceptives may decline after the age of 50.
Ovarian cancer's death rate and frequency have declined over the last 30 years, particularly among middle aged women. During this time, numerous studies have shown that childbirth and oral contraceptives reduce the risk of ovarian cancer. For these reasons, researchers explored the effect of long-term oral contraceptive use in postmenopausal women.
"The data suggest that use of oral contraceptives, for four or more years before menopause, decreases the risk of ovarian cancer risk by as much as one-half," says Suzanne Gnagy, BS, a research assistant with the Department of Health Research and Policy at Stanford University School of Medicine. "But the data don't address whether high-dose formulations are more protective than low-dose formulations."
Doctors say that low-dose formulations may not suppress ovulation. "Research shows that suppressing ovulation reduces the risk of ovarian cancer," says Lorraine King, MD, a reproductive endocrinologist and associate professor of obstetrics and gynecology at Jefferson Medical College in Philadelphia. "But low-dose formulations may not suppress ovulation to the same degree as high-dose formulations." King tells WebMD that low-dose formulations are used to help control the symptoms of menopause.
During the three- to four-year period before menopause when estrogen levels begin to drop, women can benefit from low-dose formulations to control hot flashes and other symptoms, says King. "But oral contraceptives increase their risk for ... blood clots. So I prescribe low-dose therapy for about two years."
The oral contraceptive needs of individual women vary -- some need contraception, some need relief from premenopausal symptoms, and some are concerned about their risk of developing various cancers. Therefore, you should discuss with your doctor your personal contraceptive needs after a medical evaluation.
For the study, researchers used data from previous national studies and calculated the rate of childbirth, use of oral contraceptives, the frequency that ovarian cancer occurred, and its fatality rate for women who were between the ages of 30 and 64 during the study. The data showed that women born after 1935 had fewer children, that women born after 1925 used oral contraceptives for a longer time period, and that the death rate from ovarian cancer has declined in all age groups since 1970.
By combining these trends, the researchers developed a model to estimate how many women would develop ovarian cancer. In premenopausal women, the actual rate of ovarian cancer matches the rate predicted by the model. But in postmenopausal women, the actual rate is higher than predicted. In response to this finding, the lead author says the protective effect of oral contraceptives may decline after the age of 50.
King says some questions still remain, and the researchers agree. "To clarify the long-term protective effect of oral contraceptives, more studies are needed," says Gnagy. "Current research is underway to explore the link between lifestyle and ovarian cancer."
The study was supported in part with a grant from the National Institutes of Health.