Timing of hormone therapy influences breast cancer risk

Health 31 Jan 11 Women starting hormone therapy at the time of menopause have a greater risk of breast cancer than those starting therapy later, an Oxford University study has found. The results, published in the Journal of the National Cancer Institute , add to our picture of how the balance of risks and benefits of hormone therapy vary for individual women. But there is no need for any immediate changes in the way hormone therapy is currently prescribed, the researchers say. Dr Jane Green, one of the co-authors of the study, said: 'The main new finding is that the risk of breast cancer in women taking hormone therapy for the menopause depends on how soon after menopause therapy is started. 'Women starting hormone therapy within five years of the menopause - including those starting before or at menopause - have a higher risk of breast cancer than women starting therapy five or more years after menopause.' This new finding adds to the now well-established effects of hormone therapy on women's risk of breast cancer, Dr Green explains. These include a greater risk of cancer with combined oestrogen-progestagen therapy than with oestrogen alone; an increased risk among women currently on hormone therapy that falls off rapidly once they stop; greater risks the longer hormone therapy is used; and a greater relative risk in lean women than in those that are obese. But few studies have looked at the timing of hormone therapy as a risk factor, although two previous studies suggested the interval between menopause and initiating hormone therapy may influence breast cancer risk.