Sales of supplements for menopause symptoms are likely to surge in coming months, after a major UK study finds that combination hormone replacement therapy (HRT) could double the risk of breast cancer.
The study, involving over a million women in the UK and thought to be the largest ever done on HRT, showed that risk of breast cancer was four times greater with use of combination (progestagen-estrogen) HRT compared to estrogen-only therapy. But it is also the first to report an increase in risk of death from breast cancer for HRT users compared with women who have never used HRT.
Only last year, a US trial revealed a strong association between combination HRT and risk of ovarian cancer, as well as coronary heart disease and blood clots. The dramatic results led the Women's Health Initiative (WHI) group to call an end to the research, just five years into the eight-and-a-half year study.
Since then, sales of supplements including herbal extracts such as black cohosh and red clover, or soy isoflavones, have been steadily increasing around the world. The new study should spur further trials to record the efficacy of such plant extracts. Until now, results have been conflicting, even if some show considerable potential.
The Million Women Study lead by Valerie Beral and colleagues from Cancer Research UK's epidemiology unit in Oxford, UK, investigated the effects of specific types of HRT on incident and fatal breast cancer. Around a million UK women aged 50-64 years were recruited into this study between 1996 and 2001, and half of these had used HRT. Out of the participants, 9,364 got breast cancer and 637 died from breast cancer after an average of 2.6 and 4.1 years of follow-up.
Current users of all types of HRT including oestrogen-only, combined estrogen-progestagen, and tibolone (synthetic HRT) were at an increased risk of breast cancer compared with never users, the researchers report in the current issue of The Lancet.
And the risk of breast cancer increased with the duration of HRT use, an effect that appeared to wear off within a few years of stopping therapy however. Current users were also at a 22 per cent relative increase risk of death from breast cancer compared with never-users, said the UK team.
The investigators write that the use of HRT by women aged 50-64 years in the UK over the past decade has resulted in an estimated 20,000 extra breast cancers, of which 15,000 are likely to be associated with oestrogen-progestagen HRT.
In an accompanying commentary, Chris van Wheel from the University of Nijmegen, The Netherlands, said: "The problem is in those women who are already, often for a long time, taking HRT- estimated at between 20 per cent and 50 per cent of all women 45-70 years of age in the western population. This group should discontinue HRT use as soon as possible."
The study looks set to trigger a major rethink in the way the menopause is treated by both health professionals and consumers, with natural options looking increasingly preferable.