Colorectal cancer is the second most common cause of death from cancer in the United States. The most effective way to reduce your risk of colon cancer is with a colonoscopy. Treatment works best when the cancer is found early. Screening tests can help find polyps and can find cancer that is still in its early stages and hasn't spread yet. Colonoscopy is recommended for adults starting at age 45, and earlier for those at high risk. People at risk by race/ethnicity or family history should check with their doctor about specific screening recommendations that address those risks.