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Colon and colorectal cancer

Colon and rectal (or colorectal) cancer starts in the colon (large intestine) or rectum (the last 8 inches of the colon). According to the American Cancer Society, colorectal cancer is one of the leading causes of cancer-related deaths in the United States. However, early diagnosis often leads to a complete cure.

Common causes

You have a higher risk for colon cancer if you:

  • Are older than 60
  • Are of African-American or eastern European descent
  • Eat a diet high in red or processed meat
  • Have cancer elsewhere in the body
  • Have colorectal polyps
  • Have inflammatory bowel disease (Crohn's disease or ulcerative colitis )
  • Have a family history of colon cancer
  • Have a personal history of breast cancer
  • Use cigarettes and alcohol


Many cases of colon cancer have no symptoms. These symptoms may also be caused by other, less serious conditions, so it is important to talk to your doctor if you experience any of them:

  • Abdominal pain and tenderness in the lower abdomen
  • Blood in the stool or black, tar-like stools
  • Diarrhea, constipation or other change in bowel habits
  • Intestinal obstruction
  • Narrow stools
  • Unexplained anemia
  • Weight loss with no known reason


With proper screening, colon cancer can be detected before symptoms develop, when it is most curable.

A fecal occult blood test is a test for blood in a stool sample.

Colonscopy and sigmoidoscopy are examinations of the inside of the intestine using an endoscope, a long, thin, flexible tube equipped with a light and a video camera, which records a view of the inside of the intestine, for your doctor to review.

Blood tests, including a complete blood count (CBC) to check for anemia and liver function tests also may be done.

If your doctor learns that you do have colorectal cancer, more tests will be done to see if the cancer has spread. This is called staging. CT or MRI scans of the abdomen, pelvic area, chest or brain may be used to determine the stage the cancer. Sometimes, PET scans are also used.

Stages of colon cancer are:

Stage 0: Very early cancer on the innermost layer of the intestine
Stage I: Cancer is in the inner layers of the colon
Stage II: Cancer has spread through the muscle wall of the colon
Stage III: Cancer has spread to the lymph nodes
Stage IV: Cancer has spread to other organs  


A group of physician specialists will review your case and develop treatment plans to meet your needs. The group may include:

  • Medical oncologists (cancer specialists)
  • Gastroenterologists (gastrointestinal specialists)
  • Surgeons
  • Radiation oncologists (specialists in treating cancer with radiation)

Doctors almost always use surgery to treat colon and rectal cancer. They can often remove and cure it when they find and treat it early.

If the cancer has spread into the wall of the colon or further, you may also need radiation or chemotherapy.

Radiation therapy depends partly on the stage of the cancer. In general, treatments may include:

  • Chemotherapy to kill cancer cells
  • Surgery, often removal of all or part of the colon (colectomy) to remove cancer cells
  • Radiation therapy to destroy cancerous tissue

Treatment for the stages of colon cancer

Very early or Stage 0 colon cancer may be treated by removing the cancer cells, often during a colonoscopy. For stages I, II, and III cancer, more extensive surgery is needed to remove the part of the colon that is cancerous

Almost all patients with stage III colon cancer should receive chemotherapy after surgery for approximately six to eight months. Chemotherapy is also used to treat patients with stage IV colon cancer to improve symptoms and prolong survival.

For patients with stage IV disease that has spread to the liver, various treatments directed specifically at the liver can be used. This may include:

  • Burning the cancer (ablation)
  • Cutting out the cancer
  • Delivering chemotherapy or radiation directly into the liver
  • Freezing the cancer (cryotherapy)

Although radiation therapy is occasionally used in patients with colon cancer, it is usually used in combination with chemotherapy for patients with stage III rectal cancer.


Cancer is, in many cases, a treatable disease if caught early. How well you do depends on many things, including the stage of the cancer. In general, when treated at an early stage, the vast majority of patients survive at least 5 years after their diagnosis. However, the 5-year survival rate drops considerably once the cancer has spread.


Colon cancer can almost always be caught in its earliest and most curable stages by colonoscopy. Almost all men and women age 50 and older should have a colon cancer screening. Patients at risk may need screening earlier.

Colon cancer screening can find precancerous polyps. Removing these polyps may prevent colon cancer.

Dietary and lifestyle modifications are important. Some evidence suggests that low-fat and high-fiber diets may reduce your risk of colon cancer.