Wednesday, January 26, 2011


Even as kids growing up in the 1930-40s we knew smoking wasn’t good for you. In fact, we said if you smoked a cigarette you were driving another nail in your coffin. Sure enough after years of research it was decided that smoking does cause lung cancer and other problems. But, the question for today is does it increase breast cancer?

In a new paper just published the answer is: Yes and No and Maybe (Xue et al 2011 Arch Intern Med 171 125). As usual, this epidemiological study presents marginal data some of which they say show a “modest” increase risk of breast cancer associated with smoking.

For example: for women who never smoked the absolute risk of breast cancer was 0.28% compared to those who smoked, 0.30% or an increase of 0.02%. Or put another way the odds are 28/10,000 if you don’t smoke and 30/10,000 if you do. Such a small difference cannot be considered significant, even though they say it is.

Other subgroup studies indicated some more marginal, just barely significant data. The more interesting subgroup study suggested that smoking before menopause was associated marginally with a slight increase incidence of breast cancer, whereas smoking during the postmenopausal period was associated with a consistent and significant decrease.

The most interesting data which the authors fail to discuss is in a subgroup consisting of women who smoked and took postmenopausal hormone therapy: The surprising answer: Whether they smoked or not there was no increase in breast cancer. How could the authors not mention that this finding contradicts the prevailing and incorrect assumption that postmenopausal hormone treatment increases the incidence of breast cancer??? Could it be that they are embarrassed by the possibility that they were wrong about this important point???

At any rate, the paper is just another example of the kind of epidemiological data which should never have been published. All of you smokers out there need not worry about breast cancer, that is the least of your worries.

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