Once again we are returning to the question of whether menopausal hormone replacement therapy (HRT)increases breast cancer risk.
The recent issue of Journal of Family Planning and Health Care contains an article by two researchers who argue that the data used in the previously reported Million Women Study is too flawed to support its widely-heralded finding that HRT use increases breast cancer risk.
The Million Women Study is an observational study that found that women who used estrogen and progestin had an increased risk of developing breast cancer. It is well understood that epidemiologic studies like the Million Women Study can only prove correlations, and not cause and effect. In fact, there are several observational studies that supported the use of HRT to prevent heart disease, a finding that was not born out when randomized trials were done.
Moreover, the Million Women Study is not the only study to come to this conclusion nor is it the key study most researchers point to when talking about the risks associated with HRT. That study is the Women’s Health Initiative, a randomized placebo-controlled trial that was specifically designed to measure the benefits and risks of menopausal hormone therapy and that was stopped in July 2002 when an interim data analysis indicated that the risks of this therapy outweighed any benefits the drugs had to offer.
The WHI confirmed what observational studies like the Million Women Study had found. And it was the WHI that shifted the way women and their doctors think about HRT. Furthermore, over the past decade, a number of studies have been published that have shown that as large numbers of women stopped using HRT, breast cancer rates went down.
Unfortunately, this article appears to be getting quite a bit of media play. Why do I say unfortunately? Because pointing out the problems with the Million Women Study in no way invalidates the WHI results, nor does it change the advice we have been giving women for the past decade: only use menopausal hormones if you need them to help with menopausal symptoms, like hot flashes, take the lowest amount that is effective, and only stay on them for as short a time as necessary.