Medical Matters/Dr Muiris Houston: The publication this month of the UK Million Women Study has changed the ground rules for the prescription of hormone replacement therapy (HRT).
Until now the standard advice to women considering HRT was that the jury was out on a link between oestrogen and progesterone treatment and the risk of developing breast cancer. With this major study, that is no longer the case. An unequivocal link between HRT and breast cancer has been proven.
What is especially important about the research, published in the Lancet, is that it was set up to examine the effects of different types of HRT on the incidence of breast cancer. By recruiting a million women aged between 50 and 64, Cancer Research UK's epidemiology unit at Oxford University made sure the study would be large enough to answer what has been a six-million-dollar question in medicine for some time.
The study has a number of key findings. Women taking the most common form of HRT, combined oestrogen- progesterone therapy, are twice as likely to develop breast cancer as women who are not on HRT. Women taking oestrogen-only HRT, prescribed for patients whose wombs have been removed, are 30 per cent more likely to develop breast cancer compared with women not on HRT. The risk of breast cancer is unrelated to the type or dose of HRT prescribed, and the risk is also the same whether the drug is taken orally, by skin patch or intradermally.
The increased risk of breast cancer becomes apparent within two years of starting treatment and rises with increased duration of use. Also, breast cancer risk begins to decline when HRT is stopped, within five years reaching the same level as that for women who have never been on HRT.
Most women prescribed HRT take the combined hormone preparation. Progestogen is added to the preparation to prevent women getting cancer of the womb; it is therefore not required in women on HRT post-hysterectomy. (As for the absolute risk of getting breast cancer from combined HRT, for every 1,000 postmenopausal women who take HRT for 10 years, 19 additional breast cancers will occur over and above the expected incidence of the disease for that age group.)
So what should you do if you are on HRT? An early visit to your GP is a must, to discuss the individual risk factors in your case. As a general guide, however, if you have been on HRT for two years or more you should seriously consider coming off it. It is now abundantly clear that HRT must be considered only for the short-term alleviation of the symptoms of menopause. Discussing the implications of the research, Chris van Weel, a Dutch professor of general practice, says: "The problem is in those women who are already, often for a long time, taking HRT. This group should discontinue HRT as soon as possible."
There is no need to panic if you have been on HRT for some years. Most women in this category are aged between 50 and 64 and are eligible for the national breast-screening programme. It is worth becoming more breast aware and consulting your GP if you notice changes in your breasts. Our symptomatic breast services are second to none. Combined with the national roll-out of BreastCheck, an effective safety net will be in place to deal with the fallout from the British research.
Is there any alternative for women seeking relief from unpleasant menopausal symptoms? Certainly, many alternative health products claim to be beneficial. The scientific evidence to support these claims is generally poor, however. A review in the Annals Of Internal Medicine, which looked at the use of alternative treatments for menopausal hot flushes, found 10 clinical trials of herbal treatments. Only one product, black cohosh, from the buttercup family, demonstrated a benefit. The authors warn, however, that nothing has been published about the remedy's long-term safety. One expert recommended using it for a maximum of six months. Ginseng, evening primrose oil and red clover were found to be no more effective than a placebo. In terms of scientific proof, the alternatives to HRT are limited.
Perhaps the major lesson from both the Million Women Study and last year's Women's Health Initiative research into HRT (which linked the treatment to heart disease) is the need to fund long-running trials of medication independent of the pharmaceutical sector. Short-term observational studies aimed at ascertaining the benefits of any medical advance must be treated with caution.
You can e-mail Dr Muiris Houston at mhouston@irish-times.ie. He regrets he cannot answer individual queries