Colon cancer is the second leading cause of cancer death in the United States, reports the National Cancer Institute. It’s important to begin screening for colorectal cancer starting around age 50. Your doctor can use a colonoscopy to check for cancerous growths in your colon. They will also check for polyps, a type of noncancerous growth. Certain types of polyps can develop into cancer at a later time. Ask your doctor how often you should have a colonoscopy conducted.