Colorectal Cancer: A Brief Overview

The colon and rectum are part of the digestive tract. Together, they make up the large intestine. The colon is approximately six feet in length and is composed of the cecum, the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The main function of the colon is to absorb water and nutrients from food.

The rectum is the last part of the large intestine. About ten to twelve inches in length, the rectum stores the waste material until it is eliminated from the body.

Colorectal cancer can occur in any part of the colon or in the rectum. Over 95 percent of colorectal cancers are adenocarcinomas that develop from changes in cells that result in the growth of a polyp—an abnormal growth of tissue.

 

Like most other cancers, the cause of colorectal cancer is unknown, although certain risk factors such as age are believed to increase the risk of developing it.

Nearly all colorectal cancers develop from benign polyps. These polyps, called adenomas, develop over a long period of time before finally becoming cancerous lesions.

Age seems to be a major risk factor for colorectal cancer. The risk of developing colorectal cancer increases greatly over the age of fifty.

Other risk factors of colorectal cancer include:

In its early stages, colorectal cancer has no symptoms. The optimal time to diagnose the disease is in its early stages when it's still curable but, without the proper screening, the likelihood of early detection is slim.

Even in the later stages of colorectal cancer, symptoms are not always present. If they are, people with colorectal cancer may experience symptoms such as:

If you're experiencing a number of these symptoms, see your doctor as soon as possible.

The cancer is staged depending on the size of the tumor and the extent to which the cancer has spread. Many systems are used to describe the staging of colon or rectal cancer, but the TNM system is the most popular system.

The stages normally range from I through IV, with I being an early stage of the cancer and IV being the latest and most advanced stage of the cancer.

Prognosis for an early-detected colorectal cancer is very good, and the cancer is often completely curable. If the cancer is detected in the later stages of development, the cancer may not be curable. Treatment would then focus on slowing or completely stopping the spread of the cancer and alleviating symptoms.

Surgery is the main treatment for colon and rectal cancer. For colon cancer, a colectomy is performed to remove the tumor, part of the colon and nearby lymph nodes. For cancer of the rectum, the type of surgery performed is dependent on the stage of the cancer, the location of the tumor and the extent to which the cancer has spread.

For patients in the advanced stages of colorectal cancer, chemotherapy may also be used. Chemotherapy involves the injection of drugs into the blood stream that target and kill rapidly dividing cells in the body. For colorectal cancer, the drugs most often used are 5-fluorouracil and irinotecan.

Radiation therapy may be used to kill any possible remaining cancer cells or to relieve symptoms, but it is rarely used as a treatment for colorectal cancer.

Newer therapies are currently being tested. One of the more recent treatment methods is the use of manmade proteins, or monoclonal antibodies. These proteins can target and attack cancer cells, which they can identify as different from normal, healthy cells.

Resources

American Cancer Society. (updated 2005). All about colon and rectal cancer.

HealthCommunities.com, Inc. (updated 2005). Colorectal cancer.

National Cancer Institute. (updated 2004, February). A snapshot of colorectal cancer.

National Library of Medicine. (updated 2003). Colon cancer. MedlinePlus Medical Encyclopedia.