However, only 39 percent of colorectal cancer is caught early. The five-year survival rate declines to 68 percent when colorectal cancer spreads to nearby organs or lymph nodes and 10 percent when colorectal cancer spreads to distant organs or lymph nodes.

What does screening for colorectal cancer involve?

The U.S. Centers for Disease Control and Prevention recommends a screening schedule for adults age 50 and older that includes a fecal occult blood test or a fecal immunochemical test once every year. In addition, a flexible sigmoidoscopy or double-contrast barium enema every five years or a colonoscopy every 10 years should also be performed. If you have a higher risk of colorectal cancers, such as a family history of colorectal cancer, you should start screening at a younger age and you may need testing more often. For example, the American Cancer Society recommends that people with a condition called familial adenomatous polyposis begin colonoscopy during their teens.

How is the severity of colorectal cancer described?

The most common way of describing the severity of, or staging, colorectal cancer is the American Joint Committee on Cancer's TNM system. It includes information about the tumor, any involvement of lymph nodes and any metastasis, or spread to other parts of the body.

Stage 0 is also called carcinoma in situ. This occurs when cancer is found in only the innermost lining of the colon, rectum, or both. It is the least severe form of colorectal cancer.