Aspirin may help reduce the risk of colon cancer, a new study suggests, when taken in large doses over long periods of time. Researchers studied more than 47,000 men for 18 years. They found that men who took more than two standard 325 mg aspirins a week reduced their risk for colon cancer by about 21 percent compared with those who took less. Men who took six to 14 a week reduced their risk by 28 percent, and those who took more than 14 pills a week had a 70 percent decreased risk.