Colorectal Cancer
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Colorectal Cancer

(Colon Cancer; Cancer of the Colon and Rectum)

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Colorectal cancer is a disease in which cancer cells grow in the colon and/or rectum. The colon and the rectum are parts of the large intestine.

Cancer occurs when cells in the body divide out of control or order. If cells keep dividing, a mass of tissue, called a growth or tumor, forms. The term cancer refers to malignant tumors. They can invade nearby tissue and spread to other parts of the body. A benign tumor does not invade or spread.

Colon Cancer

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The cause of colorectal cancer is unknown.

Risk Factors

Research shows that certain risk factors are associated with the disease, these include:

  • Age: 50 or older
  • Diets high in beef and fat, low in fiber
  • Polyps (benign growths) in the colon and rectum (especially due to familial polyposis , an inherited condition)
  • Personal history of colorectal cancer
  • Family history of colorectal cancer, especially a parent, sibling, or child
  • Ulcerative colitis (inflammation of the lining of the colon) or Crohn’s disease
  • Long-term insulin use in people with type 2 diabetes (associated with an increased risk)
  • Other risk factors include:


Colorectal cancer often does not have any symptoms, but some symptoms associated with colorectal cancer include:

  • A change in bowel habits such as diarrhea , constipation , or feeling that the bowel does not empty completely—lasting for more than a few days in people aged 50 and older
  • Blood (either bright red or very dark) in the stool
  • Stools that are narrower than usual
  • Abdominal discomfort (frequent gas pains, bloating, fullness, and/or cramps)
  • Unexplained weight loss
  • Constant fatigue

These may also be caused by other, less serious health conditions. Anyone experiencing these symptoms should see a doctor.


The doctor will ask about your symptoms and medical history. A physical exam will be done.

Tests include:

  • Digital rectal exam—use of a physician's gloved finger to examine the rectum for lumps or growths
  • Fecal occult blood test —a test to check for hidden blood in the stool
  • X-rays (using a barium enema )— pictures of the large intestine that show polyps or other changes
  • Sigmoidoscopy —an examination of the lower colon using a lighted tube called a sigmoidoscope
  • Colonoscopy —examination of the rectum and entire colon using a lighted tube .called a colonoscope
  • Polypectomy —the removal of a polyp during a sigmoidoscopy or colonoscopy
  • Biopsy —the removal of colon or rectal tissue to be tested for cancer cells
  • Computerized tomography (CT) , magnetic resonance imaging (MRI) , or positron emission tomography (PET) —to identify the spread of the tumor outside the colon


Once colon cancer is found, staging tests are performed to find out if the cancer has spread and, if so, to what extent. Treatment depends on the stage of the cancer.

Treatments include:


Surgery is the main treatment. It requires removal of the cancerous tumor and nearby colon or rectum tissue. It may also involve nearby lymph nodes.


In most cases, the healthy portions of the colon or rectum are reconnected. Sometimes they cannot be joined. In this case, a temporary or permanent colostomy is necessary. This is a surgical opening through the abdomen into the colon. Body waste can exit here into a special bag.

Radiation Therapy

This is the use of radiation to kill cancer cells and shrink tumors. It is directed at the site of the tumor from a source outside the body. It is used alone or in combination with chemotherapy in rectal cancer.


This therapy uses drugs to kill cancer cells. It may be given in many forms, including pill, injection, and via a catheter. The drugs enter the bloodstream and travel through the body killing mostly cancer cells. It can also kill some healthy cells.


The cause of most colorectal cancer is not known. However, it is possible to prevent many colon cancers by finding and removing polyps that could become cancerous. Beginning at age 50, both men and women at average risk for the development of colorectal cancer should follow one of the five screening options listed below:

  • Yearly fecal occult blood test or fecal immunochemical test
  • Flexible sigmoidoscopy every 3-5 years
  • Yearly fecal occult blood test or fecal immunochemical test plus flexible sigmoidoscopy every 5 years
    • Of the above options, the American Cancer Society prefers the third one
  • Double contrast barium enema (x-rays of the colon and rectum) every 5 years
  • Colonoscopy every 10 years

People with any of the following risk factors should begin colorectal cancer screening earlier at age 40 and/or undergo screening more often:

  • Strong family history of colorectal cancer or polyps
  • Known family history of hereditary colorectal cancer syndromes
  • Personal history of colorectal cancer or adenomatous polyps
  • Personal history of chronic inflammatory bowel disease


American Cancer Society



Canadian Cancer Society

Colorectal Cancer Association of Canada


Casciato DA. Manual of Clinical Oncology . 5th. ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004.

Colon carcinoma. EBSCO Dynamed website. Available at: . Accessed March 18, 2008.

Colon and Rectal Cancer. National Cancer Institute website. Available at: . Accessed July 17, 2008.

National Colorectal Cancer Roundtable. American Cancer Society website. Available at: .

Last reviewed May 2008 by Mohei Abouzied, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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