Identification of subjects at risk for colorectal carcinoma through a test based on K-ras determination in the stool

Background & Aims: The gold standard for screening for colorectal carcinoma is colonoscopy. The aim of this study was to compare endoscopic results with those obtained using the noninvasive screening test of K-ras determination in the stool in a large population of patients undergoing colonoscopy. Methods: Two hundred thirty consecutive patients were studied by K-ras amplification on stool-derived DNA using polymerase chain reaction and oligomer-specific hybridization. Results: Wild-type K-ras was amplified in 103 of 230 patients (44.8%), the rate of amplification being directly proportional to the presence of an organic disease of the intestine characterized by hyperproliferating mucosa. In 30 of these 103 patients (29.1%), a K-ras mutation was found. Four of 5 with early colorectal carcinoma, all who had K-ras mutations in the tumor, were identified. In first-degree relatives of patients with colorectal carcinoma, all subjects either carrying adenomas >1 cm in diameter or multiple smaller adenomas were identified. In patients with inflammatory bower disease, the test identified the only patient with neoplastic transformation. Conclusions: The sensitivity and specificity of K-ras determination on stool-derived DNA in patients with colorectal carcinoma, in first-degree relatives of patients with colorectal carcinoma, and in patients with inflammatory bowel disease support the opportunity of a large-scale trial to validate its use as a screening test.