Testing for Colorectal Cancer Without Colonoscopy

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Most current guidelines call for colorectal testing to start at age 50 in those individuals without a family history. It should be noted that in 2018 the American Cancer Society was the first society to recommend starting colorectal cancer screening at age 45. Unfortunately, despite the guidelines, one-third of all eligible people haven’t been properly screened with one of the recommended tools.

In 2014, a new noninvasive test to detect colon and rectal cancer was approved by the Food and Drug Administration. Cologuard® was the first stool-based DNA colorectal cancer screening test available. Its development has offered hope that more people will be willing to be screened, driving down the rates of these cancers.

Over the past two decades, both the incidence of colorectal cancers in the U.S. and deaths from the disease have significantly dropped among people age 50 and older. This reduction is in no small part due to the rising rate of colorectal cancer screening. Unfortunately, as many as one third of all adults aged 50 to 75 are still not obtaining appropriate screening for colon and rectal cancer.

While Cologuard is a potentially exciting advancement, many questions remain about the optimal use of stool-based testing, which detects the presence of red blood cells and DNA mutations that may be indicative of cancer. It is important for individuals to be aware of their options for colorectal cancer screening and understand the pros and cons of each alternative.

Stool-based Testing

In the trial upon which the FDA based its approval, Cologuard was very sensitive for the detection of cancer, but it found less than half of all advanced adenomas (precancerous polyps) and even a smaller percentage of regular adenomas. People who have a positive result are advised to have a colonoscopy. Unfortunately, compared to colonoscopy, Cologuard tends to identify lesions when they are more advanced and larger.

Additional limitations of stool-based DNA testing include the fairly high false positive rate, the complexity of the test itself, the lack of well-defined screening intervals, and the greater cost when compared to current stool immunochemical tests.

Colon Cancer Statistics and Screening

Colorectal cancer is the third most common cancer and the second leading cause of cancer-related deaths in the United States among cancers that affect men and women, according to the Centers for Disease Control and Prevention.

The CDC estimates that at least 60 percent of colorectal cancer deaths could be prevented if everyone age 50 or older had the recommended screenings. Options for colorectal cancer screening include: 

  • Colonoscopy
  • Fecal immunochemical testing (FIT) for occult blood
  • Sigmoidoscopy plus FIT 
  • Stool DNA testing (Cologuard)
  • Computed tomography colonography 
  • Guaiac-based fecal occult blood testing (FOBT)

Colonoscopy Still the Gold Standard

The gold standard for colorectal cancer screening is still colonoscopy, in which your doctor uses a flexible tube to examine the inside of your colon. Colonoscopy has been successful at lowering cancer deaths by not only detecting cancer at earlier stages, but by also detecting precancerous polyps. Your doctor can remove these polyps during the colonoscopy and prevent cancer. 

Cologuard holds much promise as a screening option that is noninvasive, can produce reliable results, and provide a better patient experience. However colonoscopy remains the most sensitive test for colorectal cancer screening and the identification of precancerous polyps. Stool based tests, such as Cologuard or FIT, are reasonable alternatives for patients who are unable or unwilling to undergo a standard colonoscopy. 

Screening saves lives. Talk to your doctor about the appropriate colon cancer screening option for you.

 
author name

Ketan G. Kulkarni, MD

Ketan G. Kulkarni, MD, is a gastroenterologist with Regional GI.
Education: A graduate of Duke University and Baylor College of Medicine, Dr. Kulkarni’s special areas of interest include ERCP, EUS, and GERD.

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