Breast cancer and HRT, fact or fiction?
While the role of HRT for treatment of menopausal symptoms, treatment of early menopause and beneficial effect on bones should now be well established, the debate about HRT and breast cancer risk continues.
Following a massive drop in use of HRT after publication of the Women’s Health Initiative (WHI) trial in 2002 and Million Women Study (MWS) in 2003, an apparent drop in rates of breast cancer was claimed to provide further evidence that HRT did indeed cause breast cancer. However, researchers from Cape Town University, writing in the journal of Family Planning and Reproductive Healthcare, state that it is impossible to establish a causal link. Breast cancer rates in fact started to fall in 1999, before the drop in use of HRT and the drop seen in 2002 to 2004 was far too early to be due to the fall in use of HRT.
The same journal, in 2012, published reviews by Shapiro et al of both the WHI trial and the MWS and concluded that these studies did not in fact prove a link between HRT and breast cancer.
So can we be completely reassured that HRT does not cause breast cancer and can women go back to using HRT without any fear that it will increase their risk of this tragic disease? It seems that it is extremely unlikely that HRT causes breast cells to become cancerous, but it is possible that, if certain types of HRT (combined HRT containing estrogen and progestogen rather than estrogen alone), are taken for more than 5 years after the age of 50, there may be promotion of cancer cells which are already present in some women, but not in the majority. To add to the complexity, even within types of combined HRT, it appears that different progestogens have differing effects, some types appearing to be “breast-friendly”.
Finally, to try to understand the level of risk, it is known that drinking 2 or more units of alcohol per day, or being overweight after the menopause both provide a far greater level of risk than taking HRT for 5 years. See our downloadable diagram showing the relative risks of breast cancer with HRT, alcohol and obesity (PDF 186Kb)
No medicine is perfect and everything that we do carries some level of risk. It is essential that women who are considering taking HRT and healthcare professionals who are considering prescribing HRT should access accurate information to help them make informed choices. Currently, many women are missing out on benefits of HRT because of fear of risk but for the majority, when HRT is used appropriately, the benefits outweigh the risks.