That news appears in a study published in the Journal of the National Cancer Institute.
The researchers included James Lacey Jr., PhD, of the National Cancer Institute (NCI).
Lacey and colleagues studied more than 97,600 women who were 50-71 years old when the study started in the mid-1990s.
At the time, none had had ovarian cancer.
By the end of 2000, 214 women had been diagnosed with ovarian cancer.
Those who had used hormone replacement therapy for 10 years or longer were more likely to be diagnosed with ovarian cancer during the study.
Women who had used hormone replacement therapy for less than a decade weren't more likely to be diagnosed with ovarian cancer.
Past studies on hormone replacement therapy and ovarian cancer risk have had mixed results, the researchers note.
"The increased absolute risks appear to be small, and other risk-benefit considerations may dominate patients' and clinicians' decision-making regarding hormone therapy," Lacey's team writes.
In other words, hormone replacement therapy may not dramatically raise the risk of ovarian cancer, and women and their doctors should weigh hormone therapy's pros and cons.
"Nonetheless, these associations, if real, represent potentially avoidable risk factors for a highly fatal cancer and therefore warrant continued investigation," the researchers add.
That is, if the findings hold up, they may suggest one way to lower ovarian cancer risk.
About Ovarian Cancer
Ovarian cancer is the ninth most common cancer and the No. 5 cause of cancer death for U.S. women, according to the American Cancer Society.
Ovarian cancer is the deadliest cancer of women's reproductive system, partly because there are no proven screening tests to spot ovarian cancer in its early, more treatable stages.
Ovarian Cancer Symptoms
Early ovarian cancer often doesn't show any obvious symptoms.
According to the NCI, these symptoms may appear as ovarian cancer grows:
- Pressure or pain in the abdomen, pelvis, back, or legs
- A swollen or bloated abdomen
- Nausea, indigestion, gas, constipation, or diarrhea
- Feeling very tired all the time
Less common symptoms may include:
- Shortness of breath
- Feeling the need to urinate often
- Unusual vaginal bleeding (heavy periods, or bleeding after menopause)
Such symptoms don't necessarily mean a woman has ovarian cancer, "but only a doctor can tell for sure," states the NCI's web site.
"Any woman with these symptoms should tell her doctor," states the NCI.