Evidence from randomised trials
The most conclusive evidence for an association between
aspirin and cancer would be shown by randomised
controlled trials. However, the risks of vascular events
and cancer increase with age, and denial of vascular
benefi ts to participants in the control group of new
cancer-reduction trials would probably be judged
unethical. Nevertheless, we have gathered evidence from
previous studies, which involved the random allocation
of aspirin or other NSAIDs for purposes other than
cancer reduction.