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Balancing the risks and benefits of HRT

Obstetrics and gynaecology

Obstetrics and gynaecology

A recent paper from the influential Million Women Study has shown that the risk of developing ovarian cancer is increased by HRT use. The question is: how should these data be incorporated into HRT consultations in primary care?

A total of 1.3 million women were originally recruited to the study, beginning in 1996. Data were collected over an average of 5.3 years from nearly 950,000 women. Half the women had used HRT, 30% of whom were current users.

There were small differences between never, ex-HRT users and current HRT users. Never-users were less likely to have had a hysterectomy and to have used oral contraceptives. The differences were either considered insignificant or controlled for in the analysis.

Current HRT users were more likely to develop, and die from, ovarian cancer than never-users. It was calculated that over five years the incidence rates for ovarian cancer were 2.2/1,000 for never-users and 2.6/1,000 for current HRT users.

No increase in incidence was seen in ex-users. The incidence of ovarian cancer was unrelated to the type, formulation or mode of delivery of HRT, but did increase with longer duration of use. The relative risk of developing and dying from ovarian cancer in current HRT users compared with never-users was 1.2 (95% CI 1.09-1.32, P=0.0002) and 1.23 (95% CI 1.09-1.38, P=0.0006) respectively.

Translating these data into figures that might assist women contemplating starting or continuing HRT requires actual numbers needed to treat or harm. Over five years, one more ovarian cancer developed and one more ovarian cancer death occurred in 2,500 and 3,300 HRT users respectively compared with never-users. The increased risks were confined exclusively to current HRT users.

Statistical and clinical significance are not the same thing. Five years of HRT use does increase the risk of developing ovarian cancer by a statistically significant amount.

But when the same data are expressed in ‘numbers needed to treat or harm' the clinical significance seems less.

Of course HRT should be given at the lowest effective dose and for the minimum required duration. But this is the case for all drug prescribing. HRT remains the only really effective option for women with serious climacteric symptoms. Breast, not ovarian, cancer is its most important adverse effect. Women need accurate figures and dispassionate advice to assist in HRT decision-making. Relief of symptoms is the main indication for use of HRT, and the subjectivity of the symptoms and their response to HRT make the subject (the patient) the only person who, in the end, can decide whether the risk-benefit balance is persuasive.

Million Women Study Collaborators. Ovarian cancer and hormone replacement therapy in the Million Women Study. Lancet 2007 doi:10.1016/S0140-6736(07)60535-2

Reviewer

Dr Chris Barclay
GP, Sheffield

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