June 2016, Vol. 5, No. 5
Stool DNA Test Performs Well in Community-Based Setting
A noninvasive screening test for colorectal cancer demonstrated potential for identifying cancer and advanced adenomas in community-based patients who previously had not followed national screening recommendations.
Almost 90% of patients completed the Cologuard stool DNA test when offered the option, and 15% had positive tests that led to referral for diagnostic colonoscopy. Although none of the 393 patients in the study had undergone screening colonoscopy within the previous 10 years, 90% of those with a positive stool DNA test followed through with the colonoscopy referral.
Colonoscopy revealed cancer in 4 patients and advanced adenomas in 21, as reported at the American Association for Cancer Research Annual Meeting.
“The availability of the multitargeted stool DNA test provided significant medical benefit to our previously screening-noncompliant Medicare population,” said Mark Prince, MD, Director of Gastroenterology at USMD Physician Services in Dallas, TX. “Patients with clinically critical advanced colorectal neoplasia were identified in this cohort due to high compliance with both stool DNA screening and follow-up diagnostic colonoscopy.”
Although derived from a retrospective chart review, the results provided “real-world” support for the pivotal multicenter trial that led to FDA approval of the stool DNA test as a screen for colorectal cancer. The pivotal trial, involving 10,000 patients, showed the test had 92% sensitivity for detecting colorectal cancer, 42% sensitivity for colonic adenomas, and an 87% specificity. Number-needed-to-treat values were 154 with colonoscopy, 166 with the multitargeted stool DNA test, and 208 with the fecal immunochemical test (N Engl J Med. 2014;370:1287-1297).
Whether the results from the prospective trial might be extrapolated to the community setting remained unclear. To investigate the issue, Dr Prince and colleagues reviewed medical records of patients in the USMD Health System and identified 393 Medicare beneficiaries who had not undergone screening colonoscopy in the previous 10 years or completed a fecal occult blood test within 1 year.
The patients had a mean age of 69.8 years, and women accounted for 64% of the study population. All of the patients had an average risk for colon cancer.
Dr Prince said 77 providers offered the stool DNA test to the 393 screening-noncompliant patients, and 347 completed the test, representing a compliance rate of 88.3%. The test yielded positive results in 51 of the 347 patients (14.7%). All patients with positive results were referred for colonoscopy, and 46 (90.2%) complied with the recommendation. Of the remaining 5 patients, 3 refused colonoscopy and 2 were lost to follow-up.
Colonoscopy results for the 46 patients showed that 4 had colon cancer, 21 had advanced adenomatous polyps, 9 had nonadvanced adenomas, and 12 patients had neither polyps nor cancer. None of the patients had symptoms prior to the positive stool DNA test.
The results supported those of the pivotal trial, suggested good compliance with the test in the community setting—even among patients who have been noncompliant with other screening methods—and provided additional evidence that “colon cancer screening saves lives,” said Dr Prince. “Colonoscopy is the best form of colon cancer screening, but for patients who will not have a colonoscopy, a noninvasive screening test like Cologuard is needed.”
However, he cautioned that every patient with a positive stool DNA test should be referred for colonoscopy, which remains the definitive method for detecting colon cancer and advanced adenomas of the colon.
Dr Prince added that the applicability of the result to patients with private insurance remains unclear.
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