HORMONE replacement therapy raises the risk of getting breast cancer by a third — double previous estimates.
And the danger remains for more than a decade after the menopause treatment, a major study shows.
It means HRT is to blame for one in 20 breast cancers, equivalent to about 3,000 cases a year in Britain, the researchers say.
It also makes it one of the major triggers for the disease after smoking, they warn.
Researcher Professor Richard Peto, from Oxford University, said: “I don’t want to be alarming but don’t want to be reassuring either.
“It’s going to be responsible for more than five per cent of all breast cancers.”
The average age for menopause in the UK is 51, with common symptoms including hot flushes, mood swings, loss of sexual desire and vaginal dryness.
ONE MILLION ‘AT RISK’
About 1million women in Britain use HRT to help tackle the effects of the menopause and to boost bone health.
But the latest study shows 8.3 per cent of women who have the most common form for five years would get breast cancer over the next 20 years. The rate for those who had no treatment was a third lower at 6.3 per cent.
It was also thought that once a woman stopped the treatment the added risk fell away. But the study of 569,000 women showed it lasted for a decade.
Regulators in Europe and the USA recommend HRT is used for the shortest time needed.
But guidance from the NHS watchdog encouraged greater uptake and did not specify a limit.
Researcher Professor Valerie Beral said: “These are real risks.
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“We really are concerned that many GPs are saying this is something that you don’t have to worry about.”
But Professor Martin Marshall, of the Royal College of GPs, said: “There is still a lot of evidence to suggest that HRT is safe and effective.”
Breast cancer affects around 55,000 Brits a year – with nearly 12,000 dying.
WOMEN ‘IGNORANT’ OF HPV DANGERS
NEARLY half of women wrongly believe they are safe from the main cause of cervical cancer if they are in a long-term relationship, a poll suggests.
The human papillomavirus (HPV) is responsible for almost all cases.
But 48 per cent of women say they are not at risk while in a lengthy monogamous relationship.
However symptoms can remain dormant for years while women — and men — can get reinfected several times.
Some 21 per cent did not even know HPV was transmitted sexually.
Vicki Bokor Ingram, of Roche Diagnostics UK & Ireland, a pharmaceutical firm which polled 1,500 women, said the findings were “dangerous”.