ASPIRIN REDUCES THE INCIDENCE OF COLONIC-CARCINOMA IN THE DIMETHYLHYDRAZINE RAT ANIMAL-MODEL

Background: Epidemiological studies in humans suggest that regular use of non-steroidal antiinflammatory drugs (NSAIDs) especially aspirin significantly decreases the risk of developing colorectal cancer. Aims: The purpose of this study was to investigate the effect of aspirin on colonic carcinogenesis using the dimethylhydrazine (DMH) colonic cancer model in rats. Methods: Groups of animals were given daily doses of aspirin either 0, 5, 30 or 60 mg/kg for 18 weeks. Half of each group also received 18 x 30 mg/kg/wk injections of DMH. Results: Aspirin at doses of 5, 30 or 60 mg/kg/dy had a progressive effect on the reduction of tumour numbers and the percentage of rumours greater or equal to 5 mm in diameter. Aspirin at doses of 30 and 60 mg/kg/dy significantly reduced tumour incidence. Conclusion: These findings support the epidemiological studies in humans. The rat DMH model would appear to be suitable for investigating the mechanism of action of aspirin in reducing colonic tumour formation.