Published by Oxford University Press on behalf of the International Epidemiological Association © The Author 2007; all rights reserved.
Commentary: Aspirin and colorectal cancer—an epidemiological success story
Stroke Prevention Research Unit, University Department of Clinical Neurology, Radcliffe Infirmary, Oxford, UK.
*Corresponding author. Stroke Prevention Research Unit, Department of Clinical Neurology, Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, UK. E-mail: peter.rothwell@clneuro.ox.ac.uk
Accepted 29 August 2007
| The first 150 words of the full text of this article appear below. |
Colorectal cancer is the second most common cancer in developed countries, with a lifetime risk of 5%, and about one million new cases worldwide each year.1 Treatment is often ineffective and population screening by regular colonoscopy is expensive.1 Prevention is therefore the ideal.
Although there has been longstanding interest in the possibility that aspirin might reduce the risk of colorectal cancer, this effect has only recently been proven by long-term follow up of two large randomized trials of aspirin from the late 1970s and early '80s.2,3 Randomization to 
300 mg aspirin daily prevented up to 75% of colorectal cancers after a latency of approximately 10 years.4 There is still uncertainty about the effect of lower and less frequent doses of aspirin and further research is required, but having established a causal link between aspirin use and a reduced risk of colorectal cancer, it is timely to review the origins of
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Importance of long-term follow up |
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Causal associations in epidemiological studies |
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Use of observational studies to more precisely delineate treatment effects |
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