People who take aspirin are at reduced risk for colon cancer, unless they are among the four percent of North Americans who have a genetic susceptibility for colon cancer (JAMA, March 17, 2015;313(11):1133-1142). Colon cancer is the second leading cause of cancer death in the United States (after lung cancer), with 1,162,426 people living with colon and rectum cancer today.
If you have polyps in your colon or a strong family history of colon cancer, your doctor may recommend one adult aspirin every other day based on this study and others that show possible benefit. This study analyzed genetic and lifestyle data from 10 large epidemiologic studies of 17,000 people and found that aspirin appears to reduce risk for colon and rectal cancer by 30 percent. However, aspirin may increase risk in the four percent of North Americans who have a genetic risk for colon cancer. Aspirin blocks certain prostaglandins, and some metabolites of prostaglandins turn on your immunity to cause inflammation which can cause and spread cancer. Colon cancer cells make more prostaglandins than surrounding tissue and blocking certain prostaglandins prevents colon cancer. Until genetic testing for colon cancer risk is available, I would not recommend taking aspirin.