The preventive effects of low-dose enteric-coated aspirin tablets on the development of colorectal tumours in Asian patients: a randomised trial.


This clinical trial examined whether Asian patients who underwent removal of a colon polyp had a reduced risk of new tumors when they took aspirin. The authors sought to determine if the cancer prevention benefit of aspirin that has already been shown in white population, would also be evident in an Asian population.


A total of 311 patients 40-70 years-old living in Japan were selected in 2007-2009 after their pre-cancerous or cancerous colorectal tumors were removed using colonoscopy. These patients were then randomly assigned to two groups of 100 mg daily aspirin or placebo for two years. They received follow-up colonoscopy procedures searching for new tumors.


  • New tumors of the colon and rectum occurred in 37% of the patients taking aspirin and 46% in those not taking aspirin. After taking into account patient differences between the two groups, new tumors were 40% less likely in the aspirin patients. Most of the tumors discovered were pre-cancerous.

  • Non-smokers had a 63% reduction in new tumors with aspirin compared to those not taking aspirin. For smokers, however, taking aspirin doubled the number of new tumors. Smoking itself also made it more likely for new tumors to occur.

  • There were no differences in side effects between the aspirin and no aspirin groups. There were no cases of gastrointestinal bleeding in either group.


  • Aspirin safely reduced the occurrence of new tumors of the colon and rectum. In Japanese patients with past tumors removed by colonoscopy, daily, low-dose aspirin for two years lowered the risk of new tumors. This result is similar to that noted in Western countries and reinforces the benefit of aspirin in interfering with the development of colorectal cancer.

  • Non-smokers showed the greatest benefit from aspirin. It may be that smoking interferes with the ability of aspirin to prevent new tumors from occurring and adds to the risks of new tumors. The benefits of aspirin also appeared to be greater for those patients who drank less alcohol.