BACKGROUND Although colonoscopy-based screening has proven to be highly effective in detecting colorectal cancer (CRC), participation rates remain disappointing. Development of CRC is associated with a number of genetic or somatic mutations. New, non-invasive stool tests are currently being developed based on the detection of these alterations. We investigated if a non-invasive stool assay can offer sufficient sensitivity and specificity to supplement colonoscopy-based screening. METHODS We compared a combined stool assay, which incorporates fecal occult blood testing (FOBT), quantification of human DNA (hDNA) as well as detection of genetic mutations of KRAS and BRAF (Combined DNA stool assay), with commercially available FOBT and M2-PK tests in a multi-centric six-armed pre-clinical case cohort study. Seven hundred thirty-four patients were recruited prior to elective/screening colonoscopy or prior to surgery in case of a recent CRC diagnosis. According to clinical assessment and colonoscopy/histology results, the following groups were assigned: controls, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), hyperplastic polyps, adenomas, and CRC. Finally, 566 out of 734 patients (77.1%) were screened for CRC and overall gut status via colonoscopy, FOBT, M2-PK, with combined FOBT/M2-PK and the Combined DNA stool assay as described here. RESULTS All sensitivities and specificities are measured against histologically confirmed results by colonoscopy. Confirmed sensitivities for detecting colorectal cancer were 68% with FOBT, 83% with M2-PK, 90% with combined FOBT and M2-PK, and 85% with the Combined DNA stool assay. Specificities were 96% with FOBT, 61% with M2-PK, 62% with combined FOBT and M2-PK, and 92% with the Combined DNA stool assay in the control group with no pathological findings during colonoscopy. CONCLUSIONS The Combined DNA stool assay detects CRC with a significantly higher Youden Index than the other reviewed non-invasive screening options. The results also suggest that the Combined DNA stool assay represents a reliable assay for detecting colorectal cancer, sufficient to be recommended as a supplement to colonoscopy screening.
