Colon cancer is a type of cancer that begins in the large intestine (colon). The colon is the final part of the digestive tract. Colon cancer is sometimes called colorectal cancer, which is a term that combines colon and rectal cancer, which begins in the rectum. Colon cancer is the 3rd most commonly diagnosed cancer and the 2nd leading cause of cancer death. Colon cancer typically affects older adults, though it can happen at any age, men and women equally.

It begins as small, noncancerous clumps of cells, called polyps that form on the inside of the colon. Over time, some of these polyps can become colon cancers. Polyps may be small and produce few, if any symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying and removing polyps before they turn into cancer.

Stage 0 colorectal cancer is the earliest stage and stage 4 is the most advanced stage:

• Stage 0 – Also known as carcinoma in situ, in this stage abnormal cells are only in the inner lining of the colon or rectum
• Stage I – The cancer has penetrated the lining, or mucosa, of the colon or rectum and may have grown into the muscle layer. It hasn’t spread to nearby lymph nodes or to other parts of the body.
• Stage II – The cancer has spread to the walls of the colon or rectum or through the walls to nearby tissues but hasn’t affected the lymph nodes.
• Stage III – The cancer has moved to the lymph nodes but not to other parts of the body.
• Stage IV – The cancer has spread to other distant organs, such as the liver or lungs.

The 5 year relative survival rate for stage I and II colon cancer is 90%; the 5 year survival rate for patients diagnosed at stage III is 71% and stage IV is 14%. If colon cancer develops, many treatments are available to help control it, including surgery, radiation therapy and drug treatments, such as chemotherapy, targeted therapy and immunotherapy.

Sources: healthline.com, coloncancercoalition.org, mayoclinic.org