A noninvasive colorectal cancer screening test detected the disease in patients who had previously avoided more invasive screening measures, according to research presented at the AACR Annual Meeting 2016, April 16-20. The study of nearly 400 patients revealed four patients with cancers and 21 with advanced adenoma, or polyps.
"Despite the availability of various colon cancer screening options, more than 40 percent of Americans are not getting screened," said Mark Prince, MD, MBA, a director of gastroenterology with USMD Physician Services, a health system based in Dallas, Texas. "This study highlights the opportunity to expand the screening population by offering new, patient-friendly methods."
In August 2014, the U.S. Food and Drug Administration approved Cologuard, a multi-target stool DNA test (mt-sDNA) that detects the presence of red blood cells and DNA mutations that can be associated with colon cancer. In October 2014, Cologuard was approved for Medicare coverage.
A 10,000-patient, prospectively conducted clinical trial for Cologuard, which was published in The New England Journal of Medicine, showed that Cologuard is 92 percent sensitive for detecting colorectal cancer and 42 percent sensitive for precancer, with a specificity of 87 percent.
In this study, Prince and colleagues performed a retrospective medical records review of Medicare-eligible patients treated by physicians in the USMD Physician Services. The study focused on patients at average risk for colorectal cancer - those without symptoms, a personal or family history of colorectal cancer, or polyps - who were not previously compliant with recommended guidelines for screening.
"We were interested to see whether the 'real-life' experience with Cologuard in clinical practice would be similar to the results seen in the clinical trial," Prince said. The patients' clinicians offered Cologuard screening to patients who had not had a colonoscopy screening in 10 or more years, or a fecal occult blood test in a year or more. During the 12-month study period, from October 2014 to September 2015, USMD providers ordered 393 mt-sDNA studies, and 347 patients completed the test, achieving 88.3 percent compliance. Fifty-one patients, representing 14.7 percent of the total, tested positive by Cologuard and were referred for diagnostic colonoscopies.
According to Prince, 46 patients, or 90.2 percent of those referred, received the follow-up colonoscopies. Three patients refused the procedure and two patients did not respond to physicians' attempts to follow up.
Among the 46 patients who had follow-up colonoscopies, four were diagnosed with colon cancer. Twenty-one were diagnosed with advanced adenoma, or polyps; nine had non-advanced adenoma; and 12 tested negative.
Prince said the discovery of four cases of colon cancer and numerous polyps, which have the potential to develop into cancer, supported the findings of the clinical trial. He noted that none of the patients had reported any symptoms and all had previously refused colonoscopies.
"Colon cancer screening saves lives," Prince said. "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."
Colorectal cancer is the second deadliest form of cancer in the United States. This year, nearly 135,000 Americans will be diagnosed with the disease and 50,000 Americans will die of it.
Prince said a limitation of the study is that it involved only patients who were eligible for Medicare. "It will be interesting to analyze the use in commercially insured patients when insurance coverage becomes more widespread," he said. Prince also cautioned that any positive results from noninvasive screening tests should be followed up by a colonoscopy.
Prince is a speaker for Exact Sciences Corp., the maker of Cologuard.