Hormone Therapy Linked to Ovarian Cancer
April 2, 2002 -- Long-term use of hormone replacement therapy has been linked to an increased risk of breast cancer. Now a new study suggests that the risk of ovarian cancer is also moderately higher in women taking estrogen or a particular estrogen plus progestin regimen.
The findings are the latest to suggest a link between hormone replacement therapy (HRT) and certain cancers. Millions of middle-aged and elderly women take estrogen alone or estrogen plus progestin (progesterone) to relieve the symptoms of menopause and protect against bone-thinning osteoporosis. Progestin is generally given with estrogen to reduce the risk of uterine cancer in women who have not had a hysterectomy.
Researchers from Sweden's Karolinska Institute studied the use of various HRT regimens in women aged 50-75, and found that ovarian cancer risk almost doubled in those taking either estrogen alone or an estrogen plus progestin regimen in which progestin is not given every day (known as cyclic HRT). The researchers found no increased ovarian cancer risk in women taking continuous HRT, in which progestin is always given with estrogen. The findings were reported in the April 3 issue of the Journal of the National Cancer Institute.
But lead author Tomas Riman, MD, says it is too early to recommend that women on hormone replacement switch from one HRT regimen to the other. That's because some studies suggest that breast cancer risk is higher for women on continuous HRT, compared with those taking cyclic HRT.
"In this study, the highest risks were observed among women who had used estrogen replacement therapy or [cyclic] hormone replacement therapy for longer than 10 years," he tells WebMD. "This study does not answer the question of whether or not to use HRT, and based on all available information it remains each woman's choice. More research is needed to learn more about positive and negative health effects in relation to use of different HRT types."
Riman stresses that the overall incidence of ovarian cancer is still very low in women on hormone therapy. He estimates the risk to be 1.6% for women on estrogen therapy or cyclic HRT for 10 years or more, compared with an average ovarian cancer risk of 1% for all women.
The Swedish study is not the first to examine ovarian cancer risk in women on estrogen therapy. In research reported a year ago, Carmen Rodriguez, MD, and colleagues at the American Cancer Society also found that women taking estrogen therapy for more than a decade had double the normal risk of ovarian cancer.
Rodriguez tells WebMD that she is surprised by the Swedish finding of an increased risk among women on the cyclic hormone regimen. Her study did not include women on progestin therapy.
"Although we did not study it, we hypothesized that adding progestins to estrogen therapy would be protective, or that women on combined therapy would not be at increased risk," she says.
Rodriguez says the overwhelming evidence suggests that HRT does not significantly increase cancer risk when taken for just a few years.
"This is a good therapy, but the decision to take it on a long-term basis is not as clear-cut as was once believed," she tells WebMD. "We still don't have a recommendation that can apply to everyone. That is why it is so important for women to discuss the potential risks versus benefits of this therapy with their doctors."