Stool Testing for Colon Cancer Screening

Last Modified: April 9, 2010


Dear OncoLink "Ask The Experts,"

What is the latest on stool testing to screen for colon cancer? Is this ready for prime time yet?

Jenia Jenab-Wolcott, MD, PhD, Gastroenterologist at the Hospital of the University of Pennsylvania, responds:


Jill Stopfer, MS, CGC, Certified Genetic Counselor, responds:

Several tests are available for colorectal cancer (CRC) screening, these include tests used for early detection only (such as stool testing) and testes that can be used for both early detection and prevention of colon cancer by removal of pre-malignant lesions (such as colonoscopy). Stool testing relies on the premise that CRC often bleed releasing small amounts of blood or abnormal DNA into the stool. There are currently two types of stool tests:

•Guaiac test and immunochemical tests examine the stool for presence of microscopic blood, that can be done on yearly basis

•Stool DNA testing that detects several abnormal DNA markers. This is an investigational tool and not used routinely in clinical practice, and there are no recommendations on the frequency of this screening test.

Advantages of stool testing it is non-invasive with less risk for procedure related complications. Guaiac testing on yearly basis can reduce the risk of dying of colorectal cancer by 1/3.

Disadvantages of stool testing- These tests have low sensitivity for polyps and low specificity of any disease. Polyps often do not bleed and guaiac testing is less likely to detect these pre-cancerous lesions. Only 2-5% of individuals with a positive stool test actually have CRC. If a stool test is positive, you will need to follow-up with a full colonoscopy.

Therefore, the preferred method for colorectal cancer screening by the American College of Gastroenterology and National Comprehensive Cancer Network is a colonoscopy.

This question and answer was part of the OncoLink Brown Bag Chat Series, Colorectal cancer Webchat. View the entire transcript here.