To quantify the association of aspirin with risk of colorectal and other cancers of the digestive tract, researchers from Milan, Italy conducted a systematic review and meta-analysis of all observational studies published through March 2019.
The evidence revealed that regular aspirin use is associated with reduced risk of colorectal cancer (relative risk [RR] 0.73; 95% CI 0.69-0.78, 45 studies), squamous-cell oesophageal cancer (RR 0.67; 95% CI 0.57-0.79, 13 studies), oesophageal adenocarcinoma as well as gastric cardia (RR 0.61; 95% CI 0.49-0.77, 10 studies) and stomach cancer (RR 0.64; 95% CI 0.51-0.82, 14 studies), hepato-biliary tract cancer (RR 0.62; 95% CI 0.44-0.86, 5 studies), and pancreatic cancer (RR 0.78; 95% CI 0.68-0.89, 15 studies).
Aspirin was not associated with reduced risk of head and neck cancer (RR 0.94; 95% CI 0.76-1.16, 10 studies).
Risk estimates were consistent across sex, geographical areas, and other selected covariates.
For colorectal cancer, an aspirin dose between 75 and 100 mg/day conveyed a risk reduction of 10 per cent and a dose of 325 mg/day of 35 per cent.
The study is published in the Annals of Oncology.