Colon Cancer Facts

The colon and rectum are parts of the gastrointestinal (GI) system. As you eat, food drops into the stomach and gastric juices are secreted to break it down. The food and gastric juices are mixed into a thick fluid and then emptied into the small intestine. The small intestine continues to further break down the food and absorbs most of the nutrients. The small intestine joins the colon, which absorbs water and nutrients from the food matter and serves as a storage place for waste before it is eliminated through the rectum and anus. The colon and rectum together form a long, muscular tube called the large intestine. The upper 5 to 6 feet of the large intestine is the colon and the lower 10 to 12 inches is the rectum.

In most cases, colon and rectal cancers develop slowly over a period of several years. Most of these cancers begin as a growth of tissue called a polyp in the inner lining of the colon or rectum.

Adentomatous polyps may progress into cancerous lesions called adenocarcinomas; more than 95 percent of colon and rectal cancers are adenocarcinomas. Removing the polyp early may prevent progession to a cancer.

Other less common types of colorectal cancers include carcinoid tumors, gastrointenstinal stromal tumors, and lymphomas.

Gastrointestinal carcinoid tumors happen when cancer cells develop in certain hormone-making cells in the gastrointestinal system. These cancers are rare and are not discussed here.

When colorectal cancers are caught early, they have a high cure rate. Because colon cancer becomes more common as people age, doctors recommend that colorectal cancer screening tests—such as a sigmoidoscopy or a colonoscopy—be performed at regular intervals after age 50, and more frequently for people with a family history of the disease.

Colon and Rectal Cancer Stages
 

The treatment that your physician will recommend for colon or rectal cancer will be determined, in part, by the stage of your cancer, which means how far your cancer has spread. Cancer stage is determined by how far the cancer has spread through the wall of the colon or rectum, spread of cancer to lymph nodes surrounding the colon or rectum, and the spread of colorectal cancer to other areas of the body (lung, liver, brain, peritoneum, etc.)

There are four stages of colorectal cancer as defined by the National Cancer Institute:

 

Stage I

The cancer has spread beyond the innermost tissue layer of the colon wall to the middle layers.
 

Stage II

Stage IIA: Cancer has spread beyond the middle tissue layers of the colon wall or has spread to nearby tissues around the colon or rectum.

Stage IIB: Cancer has spread beyond the colon wall into nearby organs or through the peritoneum or both. The peritoneum is the membrane that lines the walls of the abdominal cavity.

Stage III

 
Stage IIIA: Cancer has spread from the innermost tissue layer of the colon wall to the middle layers and has spread to as many as three lymph nodes.

Stage IIIB: Cancer has spread to as many as three nearby lymph nodes and has spread beyond the middle tissue layers of the colon wall; or to nearby tissues around the colon or rectum; or beyond the colon wall into nearby organs or through the peritoneum or both.

Stage IIIC: Cancer has spread to four or more nearby lymph nodes and has spread: to or beyond the middle tissue layers of the colon wall; or to nearby tissues around the colon or rectum; or to nearby organs or through the peritoneum or both.
 

Stage IV

Cancer may have spread to nearby lymph nodes and has spread to other parts of the body, such as the liver or lungs.