Competing Studies on Estrogen-only Therapy
Good gosh, the way medical science is published and then reported in 10 second sound bites is enough to drive anyone to drink. I wrote last month about a new reanalysis of the Women’s Health Initiative (WHI) study published in Lancet which concluded that taking estrogen in isolation (only possible after a hysterectomy) was safe with regards to breast cancer.
Now this month, I stumbled upon a short article in USA News Health which was an analysis of the Nurse’s Health Study (NHS) of women who were 30-55 years old back in 1976 and followed from 1980 to 2008.
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 and 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 increased risk of breast cancer.
Estrogen + Progestin Increases Breast Cancer Risk
Most recently, I came across a review of our current (changing) concepts regarding menopausal hormone therapy (MHT) and breast cancer just published in the Journal of the National Cancer Institute. At least one of the authors was involved in the original Women’s Health Initiative (WHI). Of course, this review did not include discussion of the unpublished analysis of the Nurses’ Health Study. But it does point out some new and different concepts developed over the decade since the release of WHI.
What’s important to note and has remained unchanged is that estrogen plus progestin increases breast cancer risk. Sure, we’ve developed some nuances, like the fact that estrogen plus progestin’s effect on breast cancer may be increased in those starting therapy closer to menopause, is not limited to hormone receptor-positive cancers, interferes w/mammographic detection, and increases breast cancer mortality, all bad things. But we’ve also learned that (ignoring said discussion of unpublished analysis) estrogen alone reduces breast cancer risk and does not interfere with mammographic detection.
How Long On Estrogen Replacement Is Too Long?
The take home point for me is that we used the wrong progestin, medroxyprogesterone acetate, rather than bio-identical progesterone (which is available as Prometrium – and no, I have no financial stake). And in doing so, we’ve blamed the wrong entity, conjugated equine estrogen (CEE). Don’t get me wrong. I’m no big fan of CEE (I’m the doc who advocates transdermal estradiol if you really need MHT). But when you look at the logic, it seems pretty clear to me that if E+P is bad and E alone is fine, the culprit is P, not E. Let’s not toss the baby out with the bath water.
In summary, 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).