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Understanding Colon Cancer -- Diagnosis and Treatment

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How Is Colorectal Cancer Diagnosed?

Beginning at the age of 50, everyone should be screened regularly for colorectal cancer (earlier screening is recommended for some high-risk groups). There are several options.

The traditional screening routine was for the doctor to perform a digital rectal exam once a year and for you to collect three stool samples to be tested for traces of blood. Also, every three to five years you would receive a sigmoidoscopy and a double-contrast barium enema to look at the lower part of the bowel. If anything were abnormal then you would be referred for a colonoscopy. The colonoscopy is a complete evaluation of the colon and rectum with a scope or long, flexible tube similar to the sigmoidoscope but longer.

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Biopsies or tissue samples of any suspicious-looking areas can be obtained during a colonoscopy for laboratory analysis.

Now, most doctors advocate going right to colonoscopy at age of 50. However, other studies are sometimes recommended when a patient is unable or unwilling to undergo colonoscopy.

A noninvasive screening procedure called virtual colonoscopy is becoming available. It does away with the tube and instead uses spiral computed tomography, which produces a three-dimensional image of the colon after it has been emptied and partially inflated with air.

The current American Cancer screening guidelines for colon cancer in an average risk patient begin at the age of 50 and include the following options: 

  • Flexible sigmoidoscopy every 5 years, or
  • Colonoscopy every 10 years, or  
  • Double-contrast barium enema every 5 years, or 
  • CT colonography (virtual colonoscopy) every 5 years. 

Alternative screening options include include a fecal or stool tests done on a yearly basis. 

However, if you are at high risk of colon cancer due to a family history of colon cancer or polyps, screening intervals should begin earlier and be more frequent.

Any suspicious symptoms or abnormalities will alert your doctor to perform a colonoscopy to get a biopsy.

Should a biopsy confirm cancer, imaging tests using chest X-rays and CT scans of the abdomen, pelvis, and possibly chest are performed to find out whether the cancer has spread to other sites.

Blood tests will also be ordered to find out how well the liver and kidneys are functioning, to determine if you are anemic, and to measure the blood level of a substance called carcinoembryonic antigen (CEA), often found in higher-than-normal concentration in the presence of colorectal cancer, especially if it has spread.


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