Hormone therapy significantly increases cancer risk, study finds

Women who undergo hormone replacement therapy (HRT) have a significantly increased risk of developing ovarian cancer, according to a major new study.

Researchers from the University of Oxford analysed 52 previous studies involving 21,000 women found that even those who took it for less than five years raised the risk level, although it reduces once they had stopped.

The researchers estimated one million women in Britain use HRT to relieve symptoms of the menopause, and therefore, the link could affect hundreds of women each year there.

The study, published in the Lancet medical journal, has led to calls for medical guidance on HRT to be updated given the causal relationship and the Medical and Healthcare Products Regulatory Authority (MHRA) said it would look at the findings.

The researchers said: The increased risk may well be largely or wholly causal; if it is, women who use hormone therapy for five years from around age 50 have about one extra ovarian cancer per 1,000 users and, if its prognosis is typical, about one extra ovarian cancer death per 1,700 users.

The findings that ovarian cancer risk is greatest in current users of hormone therapy, falls after use ceases, and varies by tumour type, strongly suggest a causal relationship ie: that among otherwise similar women, use of hormone therapy increases the probability of developing the two most common types of ovarian cancer, and hence ovarian cancer as a whole.

At present, the WHO, European, and US guidelines about hormone therapy do not mention ovarian cancer, and the UK guidelines which are due to be revised - state only that risk may be increased with long-term use.

The definite risk of ovarian cancer that is observed even with less than five years of use starting at around age 50 is directly relevant to current patterns of hormone therapy use, and hence directly relevant to medical advice, personal choices, and the current efforts to revise UK and worldwide guidelines.

Dr Sarah Branch, deputy director of MHRAs Vigilance and Risk Management of Medicines (VRMM) Division said: Our advice has always been that the lowest effective dose of HRT should be used for the shortest possible time.

We will evaluate the findings of this study and its implications for shorter term use and update product information as necessary.

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Hormone therapy significantly increases cancer risk, study finds