Unconvincing study suggests aspirin may ward off skin cancer

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In yet another case of a provocative, but largely inaccurate headline, aspirin is a big item in the news today. The 100+ year-old drug in addition to being used for pain and fever is widely used to prevent heart attacks and strokes. But a group at Stanford University School of Medicine believes that, possibly because of its anti-inflammatory properties, aspirin may decrease the risk of malignant melanoma. However, the data reported in this study show minimal if any support for this conclusion.

The Stanford group examined self-reported data from 60,000 women (who participated in the Women s Health Initiative) over a 12 year period. There are several reasons to question the authors' findings. First, there are problems inherent in any dataset relying on self-reports a notoriously unreliable method.

Second, the study had major confounders, variables that can render data meaningless. In this case, the two most egregious were exposure to sunlight, and use of other non-steroidal anti-inflammatory drugs (NSAIDS). Furthermore, the magnitude of the effect was small, ranging from 11 to 30%, depending on the length of time that the women reported using aspirin. In observational studies with self-reported data, effects like this can be an artifact of data collection and statistical significance.

Dr. Bloom notes, If anti-inflammatory effect is the rationale for aspirin s effect, it is puzzling that other NSAIDS did not have any effect on the risk. But they did not, and this makes me question the biological plausibility of their hypothesis. Furthermore the study was restricted to post-menopausal women, who will naturally have spent more total time in the sun than younger women. Given the limitations of this study, I am far from convinced that what they are seeing is real.