Estrogen vs Breast Cancer - Now What?

Good gosh, the way medical science is published and then reported in 10 second sound bites is enough to drive anyone to drink.  Just last Monday, I wrote about a new reanalysis of the Women's Health Initiative (WHI) study published in Lancet.  Their conclusion was that taking estrogen in isolation (only possible after a hysterectomy) was safe with regards to breast cancer.

But late yesterday, I stumbled upon a short article in USA Today regarding a discussion about an unnamed study in an unnamed cancer conference that concluded that estrogen use for 10 or more years, even if in isolation, could increase one's risk of breast cancer.  But the study hasn't been published so I had to dig around a bit more.  Luckily, US News Health had a much more comprehensive article.  It turns out that this was an analysis of the Nurse's Health Study (NHS) of women who were 30-55yo back in 1976 and followed from 1980 to 2008.  

So let's compare the two studies.  The good news is that this study was funded by the National Cancer Institute (so there should be less bias) compared to Wyeth's funding of WHI (which leads to obvious bias).  The bad news is that this is an observational study, so it's only good for developing hypotheses while WHI is a randomized, double-blind, placebo controlled study, which is useful for demonstrating cause & effect.  It should also be noted that NHS has data for close to 20 years regarding their subjects, while WHI is only to 12 years at this point.  One other point to put this study announcement into perspective.  www.medpagetoday.com is one of the major professional websites that pulls together news from studies & conferences and made no mention of this discussion.  For that matter, neither did www.webmd.com.

Yet, the presenters concluded in their analysis of NHS data that even estrogen-only therapy increased breast cancer risk by 22% if used for 10-14.9 years and by 43% if used for more than 15 years, when compared to those who took no estrogen.  One bright spot is that women who took estrogen for less than 10 years did not have an increase risk of breast cancer.

So which is it?  Who's telling the truth?  This is no April Fool's joke.  I, for one, don't have the answer.  But I would posit that if you need estrogen to control your menopausal symptoms, take it (assuming no other contraindications).  Remember to check back in w/your family physician regularly because chances are you won't need replacement estrogen for 10+ years (those pesky hot flashes & night sweats (among other symptoms) frequently resolve in just a few years, although they can also last 10+ years in the unlucky few).

In the meantime, I'll keep an eye out for the peer-reviewed article and post it as soon as I can.

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