Cancer is the growth of abnormal cells in the body. These extra cells grow together and form masses, called tumors. In colorectal cancer, these growths usually start as polyps in the large intestine (colon or rectum). Colon polyps are quite common and most do not cause problems. However, if they are not detected and removed, some of them can turn into cancer.

Cancers in the colon or rectum usually grow very slowly. It takes most of them years to become large enough to cause symptoms. If the cancer is allowed to continue growing, it eventually will invade and destroy nearby tissues and then spread farther. Colorectal cancer spreads first to nearby lymph nodes. From there it may spread to other parts of the body, usually the liver. It may also spread to the lungs, ovaries and bones.

The long-term outcome, or prognosis, for colorectal cancer depends on how much the cancer has grown and spread. Experts talk about prognosis in terms of "5-year survival rates." The 5-year survival rate means the percentage of people who are still alive 5 years or longer after their cancer was discovered. It is important to remember that these are only averages. Everyone's case is different, and these numbers do not necessarily show what will happen to you. The estimated 5-year survival rate for colorectal cancer is:¹

• 90% or more if cancer is found early and treated before it has spread.
• 67% if the cancer has spread to nearby organs and lymph nodes.
• 10% if the cancer has spread to the liver, lungs, or bones.