Of all colon cancer causes, colorectal polyps is by far the most common. Rectal cancer also develops from these polyps. Colorectal polyps are growths in the rectum and colon that are non-cancerous. When these polyp cells become abnormal and multiply in volume, the result is colorectal cancer. Whether rectal cancer or colon cancer, adults over the age of 50 make up 90% of cases diagnosed. Since cancerous growths in the colon and rectum often exhibit no symptoms in the early stages, regular screening after age 50 is the best way to ensure that rectal cancer is prevented or detected in its early, most treatable stage.