Colon Cancer

(Cancer of the Colon)

by Laurie LaRusso, MS, ELS

Related Media: Lower GI Endoscopy

Definition

Colon cancer is the growth of cancer in 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.

Colon Cancer

© 2009 Nucleus Medical Media, Inc.

Causes

The cause of colon cancer is unknown.

Risk Factors

Research shows that certain risk factors are associated with colon cancer:

• Age: 50 or older
• Diets high in fat, low in fiber
• History of polyps (benign growths) in the colon and rectum
• Hereditary conditions such as familial polyposis or Lynch syndrome
• Personal history of colorectal cancer
• Family history of colon or rectal cancer, especially a parent, sibling, or child
• History of ulcerative colitis (inflammation of the lining of the colon) or Crohn’s disease
• Other risk factors include:
  • Obesity
  • High body mass index (BMI)
  • Physical inactivity
  • Diabetes
  • Smoking
  • Heavy alcohol intake
  • Diet high in red meats and low in fish

Symptoms

Colon cancer often does not have any symptoms, but some symptoms associated with colon 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
• Feeling tired frequently

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

Diagnosis

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

Tests to screen for cancer or precancerous polyps include:

• Digital rectal exam—use of a doctor'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
• Colonoscopy —examination of the rectum and entire colon using a lighted tube called a colonoscope
• Sigmoidoscopy —an examination of the lower colon using a lighted tube called a sigmoidoscope
• Barium enema —a rectal injection of barium given to coat the lining of the colon and rectum; done before x-rays, in order to create better image of the lower intestine
• CT colonography —a radiology test that looks at your large intestines

Additional tests may be done to confirm the presence of cancer, determine what stage the cancer is in and/or determine if the cancer has spread:

• Biopsy —the removal of colon or rectal tissue to be tested for cancer
• Polypectomy —the removal of a polyp during a sigmoidoscopy or colonoscopy
• Blood tests to look for anemia and markers of cancer in the blood
• CT scan —a type of x-ray that uses a computer to make pictures of structures inside the body; to identify the spread of the tumor outside the colon
• Positron emission tomography (PET) —a test that produces images showing the amount of functional activity in tissue being studied; it helps in finding out if the disease has spread outside the pelvis to other organs
• Transrectal ultrasound—an ultrasound probe that is inserted into the rectum sends out sound waves to image the tumor

Treatment

Treatment depends on the stage of the cancer but may include:

If you are diagnosed with colon cancer, follow your doctor's instructions.

Prevention

The cause of most cancers are not known. However, it is possible to prevent many colon and rectal 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 colon and rectal cancer should follow one of the five screening options listed below:

• Yearly fecal occult blood test or fecal immunochemical test
• Colonoscopy every 10 years
• Flexible sigmoidoscopy every five years
• Double contrast barium enema (x-rays of the colon and rectum) every five years
• CT colonography every five years

Be sure to discuss these cancer screening tools with your doctor to see which option is best for you.

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

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

American Cancer Society
http://www.cancer.org/

CancerCare
http://www.cancercare.org/

Canadian Cancer Society
http://www.cancer.ca/

Colorectal Cancer Association of Canada
http://www.colorectal-cancer.ca/

REFERENCES:

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

Cashen AF, Wildes TM. The Washington Manual: Hematology and Oncology Subspeciality Consult . Second edition. Philadelphia, PA: Lippincott Williams & Wilkins; 2008.

Colon carcinoma. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Accessed March 18, 2008.

Colon and rectal cancer. National Cancer Institute website. Available at: http://www.cancer.gov/ . Accessed July 17, 2008.

National colorectal cancer roundtable. American Cancer Society website. Available at: http://www.cancer.org/docroot/home/index.asp .

United States Preventative Task Force. Screening for colorectal cancer: US Preventive Services Task Force recommendation statement. Ann Intern Med. 2008;149:627-637. Epub 2008 Oct 6.

Last reviewed December 2009 by Mohei Abouzied, MD
Last Updated: 12/14/2009