As the name suggests, colon cancer, also known as colorectal cancer, starts in the cells that line the inside of the colon or the rectum. The colon and rectum make up the large intestine (also called the large bowel), which is part of the digestive system. These organs help break down food, absorb nutrients and pass waste out of the body.
Colon cancer begins when cells in the lining of the colon or rectum change and become abnormal. Abnormal cells can multiply and form small, non-cancerous growths called polyps. There are different types of polyps and not all of them have the potential to grow into cancer. The ones that do are called precancerous polyps, and they can continue to grow over a long period of time without any symptoms before they become cancer. If you have polyps you may not feel any differently at all. Screening helps detect polyps early, when the treatment of colon cancer can be most effective.
Usually, colon cancer follows a slow and predictable growth. This slow growth provides an opportunity to detect cell changes at an early stage, when treatment is much more likely to be successful.
If precancerous polyps are removed in their early stages, colon cancer can be prevented.