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Lengthy HRT Use May Up Ovarian Cancer

Risk Seen in Women Taking Hormone Replacement Therapy for 5 or More Years
By
WebMD Health News
Reviewed by Louise Chang, MD

April 19, 2007 -- Hormone replacement therapy, taken for at least five years, may make ovarian cancer more likely, a British study shows.

The finding comes from Valerie Beral, MD, and colleagues with the U.K. Million Women Study.

They invited more than a million women living in Britain to take part in the study, starting in 1996.

Beral's team found that over a five-year period, women currently using hormone replacement therapy (HRT) for at least five years were 20% more likely to develop ovarian cancer and 23% more likely to die of ovarian cancer than women who had never used HRT.

Based on those findings, the researchers write that "since 1991, use of HRT has resulted in some 1,300 additional ovarian cancers and 1,000 additional deaths from the malignancy in the U.K."

However, the American Society for Reproductive Medicine notes that short-term HRT use probably isn't harmful for women using HRT to ease menopause symptoms.

HRT Study

When the study started, the women were about 57 years old, on average. They reported their current and past HRT use. Nearly two-thirds completed a follow-up HRT survey about three years later.

The researchers excluded women with a history of cancer other than nonmelanoma skin cancer and women who had had both ovaries surgically removed. That left more than 948,000 women.

Half of the women had ever used HRT. They include 30% who currently used HRT and 20% who had used HRT in the past.

The researchers followed the women for five years, on average. During that time, 2,273 women were diagnosed with ovarian cancer and 1,591 of those women died of ovarian cancer.

HRT Study's Results

Over five years, there was one extra ovarian cancer in roughly 2,500 HRT users and one extra ovarian cancer death in about 3,300 HRT users, Beral's team notes.

The increased risk of ovarian cancer only occurred in women who currently used HRT and had done so for at least five years.

Women who had quit HRT use -- and those who had used HRT for less than five years -- weren't at increased risk of ovarian cancer, compared to women who had never used HRT.

The type of HRT didn't affect the results.

The study, published in The Lancet, doesn't prove that HRT causes ovarian cancers.

But the results held when the researchers adjusted for factors including age, time since menopause, smoking, physical activity, age at first birth, BMI (body mass index), alcohol consumption, past use of oral contraceptives, social class, and geographic location.

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