Women who use a certain type of hormone replacement therapy are twice as likely to develop breast cancer as those who do not use any form of HRT at all, research claimed today.
The study of more than one million participants found that post-menopausal women using the combined oestrogen-progestagen treatment were at a greater risk than those using other types of HRT.
Research found the risk increased by 45 per cent among users of tibolone, another form of the treatment, and by 30 per cent among users of oestrogen-only HRT.
The study showed that if a woman stopped taking HRT, within a few years her risk of developing breast cancer dropped back to that of non-users. In light of the study the Committee on Safety of Medicines has reviewed data and written to all health professionals.
Their advice, while not going as far as saying that women should stop taking HRT, says doctors should carefully discuss with their patients the risks and benefits of treatment and review each case individually.
They said the results of the study did not mean any urgent changes to women's treatment were necessary. Cancer Research UK's Epidemiology Unit in Oxford monitored more than one million women between the ages of 50 and 64 who joined the study between 1996 and 2001.
Half the women were using HRT or had done so in the past. After 2.6 years of follow-up, 9,364 cases of breast cancer were found. After 4.1 years, 637 breast cancer deaths were registered among all the women studied.
Past studies have shown a link between HRT and breast cancer risk, but this is the first and largest project to discuss the increased risks relating to different types of the treatment.
The study, published in the Lancet, said current users of HRT had a 22 per cent increased risk of death from breast cancer, compared with women who had never used HRT.
An estimated 65,000 women in the State are on HRT therapies.
PA
