The risk of ovarian cancer is increased in women who use unopposed estrogen for 10 years or more, and in those taking estrogen and progestin for 5 years or more, according to a report in The Journal of the National Cancer Institute.

The absolute risk increase for ovarian cancer related to menopausal hormone therapy is small, Dr. James V. Lacey, Jr., and colleagues from the National Institutes of Health, Rockville, Maryland, write. “Nonetheless, these associations, if real, represent potentially avoidable risk factors for a highly fatal cancer and therefore warrant continued investigation.”

The findings, they also note, “expand the range of possible risks associated with menopausal hormone therapy.”

Lacey’s team studied ties between menopausal hormone use and the risk of ovarian cancer using data from 97,638 women (ages 50 to 71 years at baseline) enrolled in the National Institutes of Health-AARP Diet and Health Study who completed two questionnaires (1995 to 1996 and 1996 to 1997).

The team identified 214 incident ovarian cancers in the cohort through the year 2000.

No association was observed between ovarian cancer and use of unopposed estrogen for fewer than 10 years.

Women who used unopposed estrogen for 10 years or more had a significantly higher risk of developing ovarian cancer than women who did not use hormone therapy.

The risk was also higher, though not significantly, among women with hysterectomy.

Overall, 51,698 of the 73,483 women with intact uteri had used no hormone therapy or only estrogen plus progestin. Compared to those who did not use hormone therapy, those with long-duration use (at least 5 years) of sequential regimens had a significantly increased risk of ovarian cancer.

Long-duration use of continuous regimens was associated with a non-significantly increased risk.

SOURCE: The Journal of the National Cancer Institute, October 2006.