Colon cancer, also called colorectal cancer, starts either in the colon or rectum, which together make up the large intestine, the final portion of the digestive system. Like other cancers, colon cancer occurs when abnormal cells begin to grow and divide uncontrollably and form a mass, called a malignant tumor, in tissues or organs. Cancerous cells from these masses can enter the bloodstream or lymphatic system and spread to other organs or tissues.

Most people have no noticeable symptoms of colon cancer before diagnosis. But when colon cancer is detected early – before symptoms appear – it is often highly treatable, so screening tests, including colonoscopy, are very important and need to be done on a regular schedule. The tests, which commonly include a digital rectal exam, a fecal occult blood test, a barium enema, and a sigmoidoscopy and colonoscopy, allow doctors to look for signs of colon cancer, including blood hidden in the stool and abnormalities such as polyps inside the colon and rectum. The tests vary in how extensive and sensitive they are – ask your doctor which is right for you.

If colon cancer advances before it is detected by screening, these symptoms can occur:

* A change in bowel habits
* Diarrhea, constipation or feeling that the bowel does not empty completely
* Blood, either bright red or very dark, in the stool
* Stools that are narrower or darker than usual
* Abdominal pain
* Weight loss with no known reason
* Fatigue and/or pallor (symptoms of anemia)
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Surgery is often required for the treatment of colorectal cancer. The surgical procedure used for colorectal cancer depends on where the cancer is located.

In right-sided cancer, the right side of the colon is removed. In left-sided cancers, the left side of the colon is removed. If a cancer is in the middle transverse colon, either the right or the left colon is removed along with the transverse colon. In rectal cancer, the rectum is removed.

If the cancer is invading the muscles that help you control your bowels, those muscles then have to be removed and a permanent colostomy created. A colostomy (stoma) is where a piece of the bowel is brought to the abdominal wall and a bag is kept over this piece to collect the stool. Occasionally, temporary stomas are created until the bowel has a chance to heal. The post-surgical use of colostomy bags is declining, however. Today, stomas do not restrict daily activities in any way.

The National Comprehensive Cancer Network (NCCN) guidelines recommend that people with rectal cancer be referred to an enterostomal therapist (a health care professional, often a nurse, trained to help people with their colostomies) as part of their initial work-up. The enterostomal therapist can address concerns about how a colostomy might affect daily activities.

In cases where the cancer is found early, surgical removal of the tumor leads to a cure in 75 percent of patients. Occasionally, early cancerous changes may be limited to a portion of an otherwise non-cancerous polyp. It is sometimes possible to remove some very early colon cancers through a colonoscope. If the cancerous polyp is in the rectum, occasionally this polyp can be removed through the anus by a simple procedure. When this is done, the surgeon does not have to cut into the abdomen.

If the cancer is not detected until a later stage, when it has spread to other tissue, individuals may be treated with chemotherapy first. Intravenous 5-fluorouracil (5-FU) in combination with leucovorin, is the chemotherapy regimen most often used to treat colorectal cancer.

There are also newer options that may be more convenient than standard intravenous treatment. Capecitabine (Xeloda) is the first oral chemotherapy treatment approved for metastatic colon cancer when treatment with fluropyrimidines alone is preferred. Oral Xeloda is inactive in pill form, but reacts chemically with a substance found in abundance in many cancers, converting it to 5-FU. Since Xeloda is most active at the site of the tumor, it may save the patient from many of the common side effects found with IV drugs.

For the treatment of cancer that has spread to distant sites such as the liver or lung, usually other chemotherapeutic agents in addition to 5-FU are given.

In addition to chemotherapy, radiation therapy is also used if tumors have developed in the rectum. Individuals may be treated with a combination of chemotherapy and radiotherapy prior to surgery for rectal cancer. This combination is used to help shrink the tumor allowing the sphincter muscles to be saved.

Two drugs, bevacizumab (Avastin) and Cetuximab (Erbitux), stop cancerous tumors from developing new blood vessels, eventually shrinking or killing the tumor. The drug cetuximab (Erbitux) has been approved for metastatic colon cancer. It can be given along with other chemotherapy drugs or alone if the patient cannot tolerate other chemotherapy drugs. Cetuximab has been proven effective in shrinking tumors and delaying tumor growth.

For patients whose colorectal cancer has metastasized to a few areas in the liver, lungs or elsewhere in the abdomen, surgically removing or destroying these metastases can help the patient live longer. Liver metastases may be destroyed by cryosurgery (freezing) or by radio frequency ablation (heating the tumors with microwaves).

If the cancer has come back (recurred) in only one part of the body, treatment may consist of an operation to take out the cancer. If the cancer has spread to several parts of the body, you may receive either chemotherapy or radiation therapy.

"FDA Approves XELODA, First Oral Chemotherapy for the Treatment of Metastatic Colorectal Cancer." http://www.rocheusa.com.

"Xeloda Fact Sheet." Roche Pharmaceuticals. http://www.rocheusa.com.

"How is Cancer Found?" American Cancer Society. Revised May 2004. http://www.cancer.org. Accessed September 9, 2004.

"Can Colorectal Cancer be Prevented?" American Cancer Society. Revised May 2004. http://www.cancer.org. Accessed September 9, 2004.

Family Colorectal Cancer Registry. Thomas Jefferson University Hospital. Jefferson Health System. http://www.jeffersonhospital.org. Accessed September 9, 2004.

"FDA Approves Erbitux for Colorectal Cancer." FDA Newsletter. U.S. Food and Drug Administration. February 12, 2004. http://www.fda.gov. Accessed September 9, 2004.

"Overview: Colon and Rectum Cancer." American Cancer Society. Revised May 2004. http://www.cancer.org. Accessed September 9, 2004.
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