Cancer of the rectum usually begins as a small polyp. While most colon polyps are benign, some do become cancerous. Colon cancer symptoms may include a change in bowel habits or bleeding, but usually colon cancer strikes without symptoms. That’s why it’s important to get a colon cancer screening test, such as a colonoscopy. If the cancer is found early, the doctor can use surgery, radiation, and/or chemotherapy for effective treatment.