Simplifying Colorectal Cancer Screenings

Colorectal cancer test screens for multiple DNA markers

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Colorectal cancer screening is supposed to start with colonoscopies at age 50, but this recommendation is often ignored. That's why the disease is often caught at later, more serious stages. A new noninvasive test could change all this.

A non-invasive stool DNA screening test has been developed that studies show is highly accurate at detecting precancerous tumors (adenomas) and early-stage malignancies.

"Get screened for colorectal cancer starting at age 50."

The stool DNA test, developed collaboratively between Mayo Clinic and Exact Sciences, Inc., has been investigated in two studies that will be published in upcoming issues of Gastroenterology and Clinical Gastroenterology and Hepatology.

Lead author David Ahlquist, M.D., of Mayo Clinic and principal investigator of both studies, says “Along with its high accuracy, this test approach could improve participation rates due to its patient-friendly features.

"The test is non-invasive; requires no bowel preparation, medication restriction, or diet change; and can be performed on mailed-in samples without the need, expense, or inconvenience of a health care visit," Dr. Ahlquist said in a news release prepared by the Mayo Clinic.

The first study, a large blinded investigation, showed that this test accurately detects multiple markers for colon cancer.

  • The test detected 87 percent of curable-stage cancers among 400 people.
  • It identified the majority of large precancerous polyps.
  • Sensitivity was: 64 percent for polyps larger than 1 centimeter (cm); 77 percent for 2+ cm; 92 percent for polyps larger than 4 cm.

Co-investigator Stephen Thibodeau, Ph.D., a genetics researcher at Mayo Clinic, says "this test appears to uniquely represent an accurate noninvasive approach to large polyp detection, which offers the promise of actually preventing cancers from developing.”

The second study compared the stool DNA test with a plasma test for methylated Septin 9 (SEPT9) and found the following:

  • The stool DNA test found 82 percent of precancerous polyps vs. 14 percent detected by SEPT9.
  • The new test identified 87 percent of cancers at any stage, compared to SEPT9's 60 percent.
  • The DNA test detected 91 percent of curable stage (stage I-III) cancers vs. 50 percent with SEPT9.
  • The plasma test had nearly four times more false-positives than the DNA stool test - 27 percent vs. 7 percent.

Dr. Ahlquist points out, "Cancerous and pre-cancer cells are shed into the stool and detected by the stool DNA test long before tumors progress to invade the bloodstream for later detection by the plasma SEPT9 screening test.”

The Mayo Clinic has disclosed that it has licensed intellectual property to and is a minor equity investor in Exact Sciences. Dr. Ahlquist is one of the inventors of the licensed technology and also serves as a scientific adviser to Exact Sciences.

Reviewed by: 
Review Date: 
January 20, 2012
Last Updated:
January 22, 2012