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

With the researchers estimating one million women in the UK use HRT to relieve symptoms of the menopause, the study’s co-author Richard Peto told the BBC the link could affect hundreds of women each year.

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 UK’s Medical and Healthcare Products Regulatory Authority (MHRA) said it would look at the findings.

Any woman on HRT who has any questions should speak to her doctor who is best placed to advise

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, i.e. that among otherwise similar women, use of hormone therapyincreases 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.

“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 worldwide guidelines.”

Sarah Branch, deputy director of MHRA’s 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.

“Women on HRT should have regular health check-ups and their need to continue treatment should be reassessed at least annually.

“Any woman on HRT who has any questions should speak to her doctor who is best placed to advise.”

Concerns over safety of HRT

• HRT was first available in the 1940s but became more widely used in the 1960s, creating a revolution in the management of menopause. HRT was prescribed commonly to menopausal women for the relief of their symptoms such as hot flushes, night sweats, sleep disturbances, psychological and genito-urinary problems – urinary frequency and vaginal dryness – and for the prevention of osteoporosis.

• In the 1990s two of the largest studies of HRT users were undertaken, one clinical randomised trial in the US (Women’s Health Initiative) and one observational questionnaire study in the UK (the Million Women Study).

The published results of these two studies during 2002 and 2003 raised concerns regarding the safety of HRT. These safety concerns revolved around two main issues: that the extended use of HRT may increase the risk of breast cancer and that the use of HRT may increase the risk of heart disease.

The results of the studies received wide publicity, creating panic among some users and new guidance for doctors on prescribing.

• After the results were published, the UK regulatory authorities issued an urgent safety restriction about HRT, recommending that doctors should prescribe the lowest effective dose for symptom relief, should use it only as a second line treatment for the prevention of osteoporosis, and advised against its use in asymptomatic post-menopausal women.

• There remains widespread confusion and uncertainty among both doctors and HRT users. Many doctors stopped prescribing HRT and many women abandoned HRT immediately, with a return of their menopausal symptoms.

The number of women taking HRT fell by 66 per cent, which has not changed so that now after more than 10 years, there has been almost a generation of women who have mostly been denied the opportunity of improved quality of life during their menopausal years.

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