According to a new study women who take hormone replacement therapy or have taken it in the recent past have a higher risk of developing ovarian cancer compared to women who have never taken it.

This risk is regardless of the duration of use, the formulation, estrogen dose, regimen or route of administration.

The study was conducted by Lina Steinrud Mørch, M. Sc., of Rigshospitalet, Copenhagen University, Denmark, and colleagues to examine the risk of ovarian cancer associated with hormone therapy use, and the results were reported in the July 15 issue of the Journal of the American Medical Association.

Around 909,946 Danish women age 50 to 79 years from 1995 through 2005 were included in the study through linkage to Danish national registers, without hormone- sensitive cancer or who had not had both ovaries removed.

During the eight year follow-up, the researchers found 3,068 cases of ovarian cancer of which, 2,681 were epithelial ovarian cancers. The researchers reported 63% of the women had not been taking HT, 22% were previous users of hormones, and 9% current users of hormones. Among the current users, 46% had used hormones for more than 7 years.

The researchers said as soon as women stopped taking hormones, the risk of ovarian cancer decreased. A 22% increased risk of ovarian cancer was seen in women who had just stopped taking hormones compared to those who were off for less than two years compared to never-users. The risk of ovarian cancer had dropped back down to normal two to four years after stopping hormone therapy. The researchers didn't find any significant difference in risk based on how long women were taking hormone therapy or the type of hormone preparation they took.

Morch said they weren't able to adjust the data to account for family history or for prior birth control use, which might result in an underestimation of the ovarian cancer risk. The researchers said the absolute risk for any one woman is still quite small calculated that for every 8,300 women, hormone therapy would result in one extra case of ovarian cancer a year.

"Our study underlines previous evidence that postmenopausal hormones increase the risk of ovarian cancer," said Morch. "The risk among women taking hormones was increased regardless of the duration of use, the formulation, the estrogen dose, regimen, progestin type or route of administration," she added.

And, although the absolute risk of ovarian cancer remained low, Morch noted, "Ovarian cancer is the most lethal of gynecologic cancers. The five-year survival rates are 40 percent. Only a few risk factors for ovarian cancer are modifiable."

In a prepared statement Wyeth, maker of two conjugated estrogens Premarin and Prempro said, "The findings in this study do not change what we already know about the benefits and risks of hormone therapy, which is based on data from multiple studies. Hormone therapy remains a good health-care choice for the appropriate woman seeking relief from moderate to severe menopausal symptoms."

Dr. Victor Vogel, national vice president of research for the American Cancer Society said, "Biologically, the ovaries are intended to be in retirement after a certain age. If you try to restimulate them, it shouldn't be surprising that there are potential adverse consequences. From an epidemiological standpoint, this is important, but for an individual woman, what's likely is that she'll never develop ovarian cancer."