Validation of an Alternative Biological Test to Increase the Detection Sensitivity of a Colon Tumour

Screening campaigns for colorectal cancer (CRC) involve two steps: the detection of occult blood in stools using a Hemoccult GAIAC test (FOBT) on three consecutive stool samples, followed by colonoscopy if the result is positive. The information quality of the Hemoccult test, however, is poor: in the asymptomatic 50 to 74 year-old population, the detection sensitivity of polyps more than 1 cm in diameter is of the order of 10 to 30% and is 35 to 50% for detecting colorectal cancers; specificity is 94 to 98% that of a complete colonoscopy. The I-FOBTs based on immunological detection and quantification of occult blood in stools are currently being evaluated; based on the threshold it can be more sensitive than FOBT, but enhances useless colonoscopies. Alternatively, with highest threshold of blood in stools, it may become highly specific and miss less advanced polyps. Faecal molecular tests based on the detection of human DNA anomalies (point gene mutations, methylation disorders of CG islets) appear to be more sensitive than the detection of occult blood in stools with no loss of specificity, but they are very expensive, thereby limiting their generalisation to the scale of population screening. A formal methylated DNA test has been validated in stools as well as in blood in a cohort of symptomatic individuals having undergone colonoscopy. The aim of the present study is to validate this test by taking advantage of the biotechnical expertise from renowned academic research teams and mass screening organisation.