Parabens and Breast Cancer

Sometimes researchers remain stubbornly wedded to their ideas even when their own work begins to unravel the fabric they have woven.  I believe such is the case with Dr. Phillipa Darbre of the University of Reading in England.  Back in 2004 Darbre achieved tabloid fame with her allegation that antiperspirants were implicated in breast cancer because they accosted breast tissue with preservatives known as parabens.  These compounds have estrogenic properties and estrogens have indeed been implicated as significant players in breast cancer. 

Darbre showed the presence of parabens in cancerous tissue taken from breast cancer patients and suggested a cause and effect relationship, buttressing her argument by pointing out that most breast cancers occur in the quadrant of the breast closest the armpit where shaving nicks would allow entry of antiperspirants most readily.  The study was small, only some twenty patients, and she had no controls.  She had no idea whether parabens were also present in the breast of healthy women.  Furthermore, she never determined if her subjects had actually used antiperspirants.  The study was castigated by many breast cancer researchers with suggestions that even a high school science fair participant would recognize the need for controls.  They pointed out that breast tumours have long been known to occur more frequently in the top quadrant of the breast closest the armpit simply because that area has the highest concentration of tissue.

Stung by the accusations, Darbre has cranked out a series of papers demonstrating the estrogenic effects of parabens and measuring their concentration in various tissues.  Her latest paper, published in the Journal of Applied Toxicology, not one of the world’s most impactive journals, furthers her attempts to forge a link between these chemicals and breast cancer.  This time she has investigated more patients, 40 of them, and took 160 samples, analyzing them for different parabens.  She did not study any samples from healthy women, in other words, still no controls.  She did, however, compare parabens concentrations in tumour areas and elsewhere. 

There was no relationship between amount of parabens detected and tumour location, an observation that runs contrary to parabens playing a decisive role.  This time she did determine whether the patients had used antiperspirants and as it turns out seven out of the forty had not.  So the parabens were coming from elsewhere; no great surprise here because these chemicals are widely used in a variety of cosmetics and foods.  Darbre clearly states that the presence of a chemical in breast cannot be taken to imply causality, which of course is true.  But she then goes on to discuss all sorts of reasons why her negative results do not rule out this possibility.  For example, she says, absolute levels of parabens may not be the main determinant of risk because of variations in individual susceptibility.  Small amounts may trigger it in some people, not in others, so there may be no correlation.  An attempt to rationalize her preconceived notions.  And what about the possibility that parabens play no role at all?  Has she considered that?  But a seductive hypothesis with which one has become identified is rarely given up even when confronted by cruel facts.

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  1. Susan Barclay Nichols posted on 02/09/2013 01:17 PM
    Thank you, Dr Joe, for injecting some sanity into this topic! I have a cosmetic chemistry blog and I'm constantly quoting you for topics like this. I only wish we could get the whole Sunday broadcast as a podcast for those of us who love you in B.C.!
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