Women who use hormone therapy after menopause may be at a higher risk of ovarian cancer, and the risk remains elevated for up to two years after women stop taking estrogen, a new study says.
The Women's Health Initiative revealed that women who took hormones long-term had a greater risk of many ills.
What's more, even a relatively short duration of hormone therapy -- less than four years -- is associated with a 30 to 40 percent higher risk of ovarian cancer in current users, according to the study, which was published Wednesday in the Journal of the American Medical Association. However, experts say this may not be as scary as it sounds.
"The risk of ovarian cancer to begin with is fairly small, so a 30 percent or 40 percent increase over a small risk is still small," says Debbie Saslow, Ph.D., the director of breast and gynecologic cancer at the American Cancer Society. "However, I'm not dismissing it because it's an often-fatal disease."
Hormone therapy has been linked to health hazards in the past. Notably, part of a long-term, government-run study known as the Women's Health Initiative was stopped early in 2002 because women who took hormones for many years had an increased risk of breast cancer, stroke, heart disease, and blood clots in their lungs and legs. Health.com: The best birth control for women over 30
Since then, the use of hormones -- once offered to millions of older women to treat menopause symptoms and to potentially protect against heart disease -- has dropped dramatically. Breast cancer rates have also dropped, most likely because of declining long-term hormone use, experts say. Women are now advised to take the lowest dose for the shortest time possible to relieve menopause symptoms.
Although a couple of large studies have also suggested that hormone therapy can increase ovarian cancer risk, it seemed as if only long-term use -- more than five years -- was the culprit and that short-term use was OK. The new study suggests otherwise.
However, women who have taken hormones in the past should know that their risk drops rapidly after they stop taking them, says study author Lina Steinrud Mørch, M.Sc., of Rigshospitalet-Copenhagen University, in Denmark.
"Women currently taking hormones seem to reduce their risk of ovarian cancer by quitting hormone use," Mørch says. "This risk warrants consideration when deciding whether to use hormone therapy, particularly if a woman has a special predisposition for ovarian cancer. She should consider not taking hormones." Health.com: 9 smart ways to keep your marriage healthy at any age
The overall risk is still low. The researchers estimate that hormones cause one extra case of ovarian cancer for every 8,300 women who take them each year. They say that hormone therapy caused 5 percent, or a total of 140 extra cases, of ovarian cancer in Denmark during the study, which ran from 1995 to 2005.
The study included 909,946 Danish women -- nearly all women in the country ages 50 to 79. Overall, 3,068 developed ovarian cancer, and, of those, 2,681 were epithelial, the most common type of ovarian cancer. Current hormone users were 38 percent more likely to develop ovarian cancer and 44 percent more likely to develop epithelial ovarian cancer, in particular, than women who had never used hormones. Women who had stopped taking hormones at some point in the previous two years had a 22 percent higher ovarian cancer risk. Health.com: How to finally fix your menstrual problems
How long the current users had been taking the hormones, the combination of hormones, and the mode of delivery -- oral, transvaginally, or via a patch -- didn't seem to matter.
Exactly how hormone therapy may increase cancer risk is not fully understood. "Hormone therapy causes an already latent ovarian cancer process to develop faster," Mørch speculates.
Saslow, who was not involved in the study, says that the new finding probably won't change current recommendations for using hormones.
"The bottom line is, we're already telling women, 'Don't use it.' If you need to use it, use it for the lowest dose and the shortest amount of time, but try not to use it." Health.com: How this mother of 3 lost more than 70 pounds
To stave off menopausal symptoms, some women are now turning to "bio-identical hormones," which are made in a laboratory from wild yams or soy; traditional hormone therapies are often derived from the urine of pregnant horses. However, bio-identical hormones have not been shown to be any safer than conventional hormone therapy, says Saslow.
Also, it's not clear if the drop in hormone-therapy use will result in a large drop in ovarian cancer cases, as has been seen with breast cancer. "Given the absolute risk, we're not going to see much drop," say Saslow. "We may see a little bit."
An estimated 21,550 new cases of ovarian cancer will be diagnosed in the United States in 2009, according to the American Cancer Society, compared with 192,000 invasive breast cancer cases. Health.com: Feeling stressed? Why you may feel it in your gut
Unlike breast cancer, there is no early screening test to detect ovarian cancer when it is in its most treatable stages, and its symptoms -- bloating, pelvic or abdominal pain, difficulty eating or feeling full quickly, and urinary symptoms -- are vague.
As a result, ovarian cancer is usually detected after it has spread outside the ovaries.
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