GPs should prescribe aspirin to patients at high risk of developing colorectal cancers, according to the authors of the first randomised controlled trial to evaluate the drug as a chemoprotective agent.
The study found that 600mg of aspirin daily for two years reduced the incidence of cancers by over 60% in patients with Lynch syndrome, a genetic disposition to develop colorectal and some other solid organ cancers.
This tallies with earlier reports that aspirin use can halve the incidence of colorectal cancers.
Researchers assigned 861 patients with Lynch syndrome either 600mg of aspirin daily or aspirin placebo for a mean of 25 months. After 57 months, there were 53 primary colorectal cancers in 48 participants, 18 of whom had been assigned aspirin. The hazard ratio by intention-to-treat analysis was 0.63 (CI 0.35 to 1.13).
Similar results were obtained with other cancers. Eighteen participants developed endometrial cancer (a Lynch syndrome cancer), of whom five were assigned to aspirin.
In all, 38 patients developed non-colorectal cancers, of whom 16 were assigned to aspirin. Adverse events did not differ between the aspirin and placebo groups.
Lead author Professor John Burn, professor of clinical genetics at Newcastle University, said: ‘The case for prescription of aspirin to this high-risk group is clear.’
‘Clinicians should consider aspirin prescription for all individuals judged to be at high risk of colorectal cancer, but taking appropriate measures to minimise adverse effects.’
The authors said it is still unclear why aspirin’s chemoprotective effect remains long after patients stop taking the medication.
‘The mechanism by which aspirin suppresses cancer development long after cessation of exposure to the drug is unclear,’ added Professor Burn.
‘The rapid progression from adenoma to carcinoma in Lynch Syndrome makes it likely that many screen-detected cancers would have begun to develop after aspirin intervention ended.’
Further research is needed to establish the optimum dose and length of treatment, the authors added.