Evidence Mounting Against HRT, Now Linked to Ovarian Cancer

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April 19, 2007 — The Million Women Study, a United Kingdom–based trial of postmenopausal women, has found that those on hormone-replacement therapy (HRT) were on average 20% more likely to develop and die from ovarian cancer than women who never received therapy. Researchers reporting today online in the Lancet say that since 1991, HRT has resulted in some 1300 additional ovarian cancers and 1000 additional deaths from the malignancy in the United Kingdom alone.

"The effect of HRT on ovarian cancer should not be viewed in isolation," comment the study collaborators, led by Valerie Beral, from the Cancer Research UK's Epidemiology Unit, in London, "especially since use of HRT also affects the risk of breast and endometrial cancer. In total, ovarian, endometrial, and breast cancer account for 39% of all cancers registered in women in the UK." The total incidence of these 3 cancers in the study population is 63% higher in current users of HRT than in never users.

As previously reported by Medscape, research published in today's issue of the New England Journal of Medicine describes a dramatic fall in breast cancer incidence that perfectly mirrors the decline in HRT use in the United States (Ravdin P et al. N Engl J Med. 356;16:1670-1674).

During an interview, the study's senior author, Donald Berry, PhD, from the University of Texas MD Anderson Cancer Center, in Houston, called it a "precipitous drop" in breast cancer incidence that started immediately after the announcement of the Women's Health Initiative results questioning the safety of the drugs. He said he was surprised by the findings. "But when I realized that stopping a cancer's fuel could slow its growth, it seemed quite reasonable," he noted.

Commenting on the 2 important findings, Ahmedin Jemal, PhD, an epidemiologist at the American Cancer Society, who has studied in this area, told Medscape these results make sense. "We know that estrogen-positive cancers tend to increase when HRT is used," he said. "It would therefore not be surprising if the drugs were playing a role in ovarian as well as breast cancer."

In this latest study assessing ovarian cancer risk, researchers looked at 948,576 postmenopausal women who did not have previous cancer or bilateral oophorectomy. They were followed for an average of 5.3 years for incident ovarian cancer and 6.9 years for death. Information on HRT use was obtained at recruitment and updated where possible. The women’s socioeconomic status, reproductive history, previous use of oral contraceptives, body-mass index, and alcohol and tobacco consumption did not reportedly alter the effect of HRT on their risk of developing ovarian cancer.

Menopause Society Says Study Will Cause Unnecessary Distress

But not everyone is concerned about the findings. Responding to the study in a news release, the International Menopause Society raised a number of criticisms of the work. "Following the previous analysis of the Million Women Study on breast and endometrial cancers, there were many reservations concerning the methodology, and these are still pertinent," the society writes. "Most epidemiologists would consider that a relative risk of 1.2 is of minimal clinical significance but will inevitably reach statistical significance with very large numbers. Risk is far better reported in absolute numbers rather than relative risk or percentage. The absolute risk for ovarian cancer in the study was only 1 extra case per 2500 women after 5 years, and mortality was 1 per 3300 over 5 years."

The International Menopause Society adds, "Such manipulation of data can only cause unnecessary distress to the many women who are benefiting from HRT." The group points out that no increase in risk was recorded in women using HRT for less than 5 years and past users had the same risk as never users.

In an accompanying comment published in the Lancet, Steven Narod, MD, from the Women’s College Research Institute, in Toronto, Ontario, writes, "A relative risk of 1.2 might be thought of as small, but enormous numbers of women have been exposed. In the Million Women Study alone, half a million women had taken HRT."

He notes, "Because current use was found to be the main risk factor, the number of new cases attributable to HRT should be a function of the number of women who are taking the drug at any given time." The editorialist points out that HRT use has declined greatly in the United Kingdom and elsewhere since the report of the Women’s Health Initiative. "With these new data on ovarian cancer, we expect the use of HRT to fall further," he writes. "We hope that the number of women dying of ovarian cancer will decline as well."

Commenting on the study, Robert Rebar, MD, executive director of the American Society for Reproductive Medicine, told reporters, "Although long-term use of estrogen appears to increase the risk of ovarian cancer, women should be reassured that short-term use for symptomatic treatment at or near the menopause is unlikely to increase the risk of ovarian cancer appreciably." He said these data, taken together with findings from the Women’s Health Initiative, provide reassurance all in all that short-term use of estrogen is not harmful to symptomatic women.

Lancet. 2007; published online April 19, 2007.

Source: http://www.medscape.com/viewarticle/555492?src=mp