Long-term HRT doubles breast cancer risk
11:00 08 August 03
Original story at newscientist.com.
The overall benefit of long-term hormone replacement therapy is under serious question, after the results of the world's largest ever study revealed significant breast cancer risks.
The UK's "Million Women Study" revealed for the first time that postmenopausal women taking a combined form of HRT are twice as likely to develop breast cancer as women who have never taken the hormone preparation.
It also confirms a smaller but marked increased risk of breast cancer in women taking oestrogen-only HRT. The therapy is used to control the symptoms of menopause and to reduce the risk of osteoporosis. HRT is very widely used in developed countries, including 1.5 million women in the UK alone.
"Twenty-thousand extra breast cancers in the last decade in the UK are likely to be attributable to the use of HRT," says Valerie Beral, who led the researchers at Cancer Research UK's Oxford epidemiology unit. Of these, 15,000 are likely to be linked to the oestrogen-progestagen combination.
The finding were published in The Lancet on Friday and the UK government's Committee on Safety of Medicines (CSM) held immediate talks to provide prompt advice to anxious women and their doctors.
"For the short-term, the benefits will outweigh the risks," says the CSM's Mary Armitage. But each woman will have to weigh up the advantages and disadvantages of the therapy with their doctor, she says, with a review of their medication at least once a year.
"We agonised over the advice we are giving, because it's not an easy answer," she says.
John Toy, medical director of Cancer Research UK stresses: "This is not a medical emergency." However, some experts are calling for an immediate halt to taking HRT for many years.
The million women followed between May 1996 and March 2001 were aged between 50 and 64. Half of the women had used HRT at some point, with half of those taking the combined hormone medication.
The researchers found that women on combination HRT during the course of the study were twice as likely to develop breast cancer than women who had never used HRT. Those women taking oestrogen-only HRT were 30 per cent more likely to develop the cancer. And the small number taking the synthetic drug Tibolone were 45 per cent more likely to develop breast cancer.
Looking over a 10-year period, the risk of breast cancer is four times greater in those taking the combination HRT compared with the oestrogen-only preparation.
Combination HRT is commonly used in Europe because, unlike oestrogen-only therapy, it does not raise the risk of endometrial cancer. "That seemed fairly reasonable until these results," says Beral.
"We have to remember that breast cancer is five to 10 times more common than cancer of the endometrium," she says. "This causes a dilemma."
The study also found that HRT increased the risks of breast cancer much earlier than thought - after only a couple of years of use. However, the good news is that the risks in women who stop HRT fall back to the normal level within one to five years.
Armitage says HRT has "huge benefits" for menopausal symptom control and prevention of osteoporosis. Emily Banks, one of the researchers at Cancer Research UK, says there is evidence that HRT prevents hip fractures and protects against colorectal cancer. But she adds: "For long term use, the adverse effects seem to outweigh the beneficial effects."
When New Scientist asked Beral, the study leader, whether women should continue with HRT long-term given the new balance of risks and benefits, she declined to comment.
And in a Lancet editorial, Chris van Weel, from the University Medical Centre Niijmegen in the Netherlands, writes that women taking HRT for a long time "should discontinue HRT use as soon as possible".
Journal reference: The Lancet (vol 362, p 414)