Mayo Clinic 2010 Annual Report
Hope for patients at risk for colon cancer
Simple stool test could help in detection and prevention
and Kevin Halling, M.D., Ph.D.
A simple stool test developed in part by Mayo Clinic physician David Ahlquist, M.D., could help in the detection and prevention of colon cancer.
As many as 1.4 million people in the United States live with inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative colitis. Medication and sometimes surgery help manage IBD for most patients, but the diseases put them at higher risk than the general population for developing colon cancer.
Finding curable colon cancers
IBD patients usually show detectable signs of disease progression, including premalignant dysplasia where cell structure shows drastic changes, or serrated polyps, a type of adenoma or pre-cancerous lesions in the bowel.
"If you don't detect the pre-cancer, you don't prevent the cancer," says Dr. Ahlquist. "Given the limitations of colonoscopies in detecting these lesions, stool DNA testing could play a complementary role to improve the effectiveness of cancer surveillance."
90 percent detection rate
During Digestive Disease Week, the annual meeting of the American Gastroenterological Association, Mayo Clinic presented the results of two studies done in conjunction with Mount Sinai Medical Center in New York and the University of Chicago.
The first study looked at 10 controls and 10 confirmed cases of either cancer or dysplasia, a pre-cancerous lesion. Researchers found that stool DNA testing was positive in nine out of 10 of the confirmed cases — five of five with cancer, and four of five with dysplasia.
"This study shows that cancer and pre-cancer in IBD can be detected noninvasively," says Dr. Ahlquist. "The 90 percent detection rate by stool DNA testing is remarkable."
Detecting serrated colorectal polyps
The second study looked at serrated colorectal polyps. Unlike common adenomas, which usually protrude from the colon lining and are easy to see, serrated polyps are typically flat and the same color as the colon lining. Because they are difficult to detect, most other screening studies have excluded them as possible precursors to cancer.
"Now they are regarded as the forerunner in roughly 30 percent of colon cancers," says Dr. Ahlquist. "Most of these are located on the right side of the colon, where screening has had less impact historically."
Because DNA testing doesn't rely on visual recognition of the hard-to-identify polyps, Dr. Ahlquist's initial study tests are promising. "We observed a 71 percent detection rate with stool DNA testing. This was significantly higher than the 7 percent rate with conventional fecal blood tests."
Effective and affordable prevention
"Detection of these important types of pre-cancer by stool DNA testing offers promise in our efforts to more effectively and affordably prevent colorectal cancer," says Dr. Ahlquist. "However, findings from both pilot studies need to be corroborated in larger studies."