Estrogen replacement therapy is linked with increased risk for ovarian cancer
Data from a large, American study on estrogen replacement therapy after menopause indicate that use of the hormone increases risk for ovarian cancer, according to an article in the July 17th issue of the Journal of the American Medical Association.
Investigators followed 44,241 women for approximately 20 years. Compared with postmenopausal women who did not use any hormone replacement therapy, users of estrogen-only therapy had a 60 percent greater risk of developing ovarian cancer. The risk increased with length of estrogen use. The women, who were followed from 1979 to 1998, were former participants in the Breast Cancer Detection Demonstration Project, a mammography screening program conducted between 1973 and 1980.
"The main finding of our study was that postmenopausal women who used estrogen replacement therapy for 10 or more years were at significantly higher risk of developing ovarian cancer than women who never used hormone replacement therapy," said James V. Lacey, Jr., Ph.D., lead author of the study from and a researcher at the National Cancer Institute (USA).
The relative risk for 10 to 19 years of use was 1.8, which translates to an 80 percent higher risk than that of non-users, and it increased to 3.2 (a 220 percent higher risk than that of non-users) for women who took estrogen for 20 or more years.
As early as the 1940s, women in the U.S. began using estrogens in high doses to counteract some of the short-term discomforts of menopause such as hot flashes, vaginal drying and thinning, and urinary tract incontinence and infections. However, after it became clear in the 1970s that women who took estrogen alone had a 6 to 8 times higher risk of developing endometrial cancer, doctors began prescribing progestin along with much lower doses of estrogen. The addition of progestin to estrogen therapy reduces the increased risk of endometrial cancer associated with using estrogen alone. As a result, it became increasingly common to prescribe estrogen-progestin therapy for women who have not had a hysterectomy.
In addition to studying the effect of estrogen use alone, Lacey and his colleagues looked at whether women using estrogen-progestin therapy were more likely to develop ovarian cancer. No increased risk was found.
Lacey commented, "Even though our data showed that women who took estrogen combined with progestin were not at increased risk for ovarian cancer, only a few women in our study who developed ovarian cancer had used estrogen-progestin therapy for more than four years. So, at this point, there simply aren't enough data to say whether taking the combined therapy has any effect on ovarian cancer."
Newly available results from a large clinical trial (also published in the July 17th issue) show increases in breast cancer, coronary heart disease, stroke, and blood clots in the lungs and legs for women on estrogen-progestin therapy for an average of 5.2 years. Positive findings associated with combined hormone replacement included fewer cases of hip fractures and colon cancer. However, because the harm was overall greater than the benefit, the trial was stopped three years ahead of schedule. The randomized trial for estrogen alone in women who have had a hysterectomy is continuing.
Lacey emphasized the complexity of weighing the various risks and benefits of hormone use. "Because hormone therapy may influence so many conditions that affect women after menopause -- cardiovascular disease, osteoporosis, breast cancer, uterine cancer, gallbladder disease, blood clots, and now potentially ovarian cancer -- we should no longer think of a woman basing her decision to use hormones on the potential risk of just one condition. Women should continue to talk to their health care providers about whether hormones might be right for them."
Lacey said that some of the unknowns concerning hormone use and ovarian cancer include duration versus dose of estrogen therapy, effect of longer duration of combined therapy, type of estrogen-progestin regimen, use of more than one type of hormone therapy, and form of estrogen administration.
Every year, about 23,000 American women are diagnosed with ovarian cancer and 14,000 women die from the disease. A woman's lifetime risk of developing ovarian cancer is 1.7 percent.
