What is Colon Cancer?

The body’s digestive system processes the food and liquids that we consume and prepares them for elimination from the body as waste. The large intestine, or colon, is part of the digestive system, along with the small intestine, esophagus, stomach, rectum (the last portion of the colon), and anus (the opening at the end of the rectum through which wastes passes).

Colon cancer is the formation of cancer cells in the colon. Colorectal cancer is the second most common cause of cancer death in the United States .

Certain people may be at greater risk for developing colorectal or gastrointestinal cancer, including those who:

  • Are over the age of 50
  • Have had other types of cancer, including an earlier case of colon cancer
  • Have family members who have had colon cancer
  • Have had colon polyps (non-cancerous growths in the lining of the colon)
  • Have had ulcerative colitis (ulcers in the colon) or Crohn’s disease (inflammation and ulcers in the colon)
  • Have genetic (inherited) conditions that might make them more likely to have colon cancer

What are the symptoms of colorectal cancer?

Most colorectal cancer patients don’t have any symptoms. However, as colorectal cancer tumors grow, the patient may develop certain symptoms, including:

  • Changes in bathroom routines (i.e., a greater incidence of diarrhea or constipation)
  • Narrow stools
  • Blood in the stool
  • Weight loss
  • Anemia
  • Other gastrointestinal problems, such as vomiting, cramps, bloating, or incomplete emptying after going to the bathroom

How is colon cancer diagnosed?

If a doctor thinks a patient may have gastrointestinal and colorectal cancer, the doctor will review the patient's medical history, family history, and symptoms, and will perform a physical examination including digital rectal exam). The doctor will order other tests if necessary, including the following:

  • Fecal occult blood test to check for blood in the stool
  • Blood tests, including blood chemistry and complete blood count, to determine the number of red blood cells, and check for anemia.
  • Examination of the colon by sigmoidoscopy or colonoscopy. For these tests, the bowel is cleaned with a solution, and an instrument (usually flexible) is inserted through the rectum to check the lining of the colon. A sigmoidoscopy is an examination of the lower colon; a colonoscopy examines the entire colon. The doctor can also use the instrument to take samples of polyps for biopsy (a small sample of tissue is removed and examined under a microscope for cancer).
  • Lower GI series. The patient is given a barium enema (barium is a substance that allows cancers or other abnormalities to stand out on x-ray), and then has a series of x-rays taken.

What are the stages of colorectal cancer?

One of the biggest concerns about a cancer diagnosis is whether the cancer has spread (metastasized) beyond its original location. To determine this, the doctor assigns a number (I through IV) to the diagnosis. The higher the number, the more the cancer has spread throughout the body. This is called "staging."

The stages of colorectal cancer include the following:

  • Stage I: The cancer has penetrated into the middle layers of the colon wall but not through it.
  • Stage II: The colorectal cancer has penetrated through the muscle wall of the colon.
  • Stage III: The cancer has moved to lymph nodes near the colon and rectum.
  • Stage IV: The cancer has spread to lymph nodes and to other sites in the body, such as the liver, lungs or lining of the abdomen (peritoneum).

How is colon cancer treated?

Treatment of colon cancer depends on the stage of the cancer, its location and on the patient’s general health. Several different types of treatment are used; sometimes different treatments are combined.

The main treatments for colon cancer are surgery and chemotherapy. Rectal cancer (cancers located in the lowest 6 inches of the large bowel) also is treated with radiation therapy.


Surgery is the treatment used most often for colorectal cancer. Colon and rectal cancers require surgery if they are to be cured. Surgery usually involves removal of the cancer and some of the surrounding tissue. In most cases, the surgeon can reconnect the remaining healthy portions of the colon (anastomosis) after removing the cancer.

If the surgeon cannot reconnect the healthy portions of the colon, a colostomy will be necessary. A colostomy is an opening (stoma) through the abdominal wall into the colon. This opening provides a new passage for waste to leave the body. The colorectal cancer patient wears a special bag to collect the waste. In most cases, the stoma and colostomy bag are temporary, though for some patients they will be permanent.

The surgical procedures for colon cancer include the following:

  • Polypectomy: polyps are removed during a colonoscopy.
  • Local excision: This procedure is performed when the cancer is in an early stage. It does not require major abdominal surgery; instead, the cancer is removed through the anus.
  • Resection: total removal of parts of the colon and surrounding tissue which requires a major surgery.

Laparoscopic Surgery

Cleveland Clinic provides state-of-the-art laparoscopic surgery for a variety of colorectal conditions, including Crohn’s disease, ulcerative colitis, diverticular disease, familial polyposis, chronic constipation, colon cancer and rectal prolapse.

A minimally invasive approach to surgery, laparoscopic procedures afford patients the benefit of smaller incisions, less pain, fewer heart, lung and wound complications and shortened hospital stay. “The best thing about laparoscopic colon surgery is that we can offer patients the results of a traditional, open surgery but with incisions that are only two inches long,” remarks Cleveland Clinic Chairman of the Department of Colorectal Surgery Victor Fazio, M.D.

Radiation Therapy

In radiation therapy, high-energy x-rays damage or destroy cancer cells in order to shrink tumors. The radiation may be delivered by special equipment that directs the radiation from outside the body (external radiation). Rarely radiation may also come from an implant, a small container of radioactive material placed into or near the tumor.


Chemotherapy drugs are cancer-killing medicines given either intravenously (injected into a vein) or by mouth. Chemotherapy might be given before surgery to reduce the size of the tumor in order to make it easier to remove. Chemotherapy may also be administered after surgery to kill any cancer cells that might be left in the body.

How are the different stages of colon cancer treated?

Treatment of colon cancer varies depending on the stage of the disease:

  • Stage I: resection and polypectomy for the smallest and for larger tumors.
  • Stage II: resection and anastomosis, sometimes followed by clinical trials of chemotherapy, radiation (or radiation for rectal cancers).
  • Stage III: resection and anastomosis followed by either chemotherapy or clinical trials of chemotherapy (Radiation is used for rectal cancers stage III).
  • Stage IV: resection and anastomosis, removal of parts of other organs to which the cancer has spread, radiation and standard chemotherapy, clinical trials of chemotherapy or experiment biologic therapy.

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