HRT and Breast Cancer Deaths – Just in Case You Weren’t Listening the First Time…

A new analysis of long term data from the Women’s Health Initiative confirms what we already knew the first time around – Use of combination hormone replacement (HRT*) is associated with a small, but real, risk of breast cancer. This new 11- year follow up data carries that knowledge out to its not unexpected conclusion – namely, that some (although not most) breast cancers can be fatal, and therefore the the use of HRT can increase breast cancer mortality.

While it may seem a bit of a “Duh”, this study was, in fact, necessary to quell the WHI critics who continued to argue that the breast cancers caused by HRT were somehow less aggressive than those occurring off HRT. (They are not.) It was also a wake up call for many women who were continuing to use HRT and thinking that somehow its risks did not apply to them. A fair number of these women appear to be coming off of HRT, at least in my practice. Others are staying the course and accepting the risks as they have been defined. Either of which is fine with me.

The spin going on around this study – both for and against HRT use – is tremendous and ultimately confusing to women.  The pro-HRT crowd (some of whom have relationships to Pharma) is using language like “The increased risk from using HRT for 5 years is the same as if your menopause occurred 5 years later”, which is technically true but so what?  The bioidentical hormone crowd (usually also selling the same) are using the study to further hype how their regimens are safer than the evil Big Pharma products – based on no data. Which leaves the rest of us to try to find ways to help our patients understand the risks, place them into perspective for themselves and make a decision about how and if to treat their menopausal symptoms.

While the breast cancer risks associated with HRT use appear to be quite real, for a individual woman, they are not that large. Here’s how I explain the risks to my patients –

There will be 7 extra cases of breast cancer and 1.3 additional breast cancer deaths for every 10,000 women per year who use HRT. Said another way, if you use HRT for 20 years, your risk of getting breast cancer will be increased by 1.4 % and your chance of dying from breast cancer will be increased by about a quarter of a percent. If you use HRT for less than 20 years, we can cut those numbers down accordingly.**

If you don’t already know it, I do have my own set of rules for prescribing HRT. This new data has not changed them.

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* HRT means estrogen and progesterone taken together, as opposed to ERT, or estrogen alone. In the WHI, ERT use was actually associated with a lower rate of breast cancer, a finding unique to this study that begs for replication before we can bless ERT as breast-safe.

** The formula I used for cumulative risk is CR = 1 – e^-IR*t ,where CR = cumulative risk, IR is the annual incidence and t is the number of years (in this case 20). If any statistician types reading this can confirm my methodology or numbers I’d appreciate it.

Graph above from JAMA. 2010;304(15):1684-1692.