QUANTITATION OF DNA FROM EXFOLIATED COLONOCYTES ISOLATED FROM HUMAN STOOL SURFACE AS A NOVEL NONINVASIVE SCREENING-TEST FOR COLORECTAL-CANCER

The only widely used screening test for early detection of colorectal cancer, the fecal occult blood test, lacks both sensitivity and specif icity because it relies upon incidental bleeding rather than the neopl astic process, With the purpose of developing a new noninvasive diagno stic approach, we quantified DNA extracted from cells isolated from th e surface of human stools by a novel procedure, Stools collected from 28 healthy individuals, 17 colorectal cancer patients, and 11 colorect al polyp patients were analyzed, A stool DNA index (SDNAI), expressed as DNA amount in nanograms per gram of stool, had a remarkable 4.5-fol d difference in mean values between colorectal cancer patients and hea lthy people of comparable age, SDNAI was 2133 +/- 407 in the cancer gr oup versus 469 +/- 65 in healthy people of the older (>50 years) age g roup (P = 0.0005), The difference was independent of tumor location an d size, If 700 ng of DNA/g of stool was taken as a cutoff SDNAI value in discrimination between older healthy people and cancer patients, se nsitivity and specificity values reached 1.00 and 0.81, respectively, Age dependence of SDNAI was demonstrated by substantially lower SDNAI values (mean, 227 +/- 41) in younger healthy individuals, Polyp patien ts sometimes displayed elevated SDNAI values, but considerable variati on was observed (mean, 1215 +/- 548), These preliminary findings indic ate that SDNAI provides a novel, simple, and powerful noninvasive test for colorectal cancer early detection and screening, The fundamental advantage of the SDNAI is that it directly characterizes colonic epith elium involved in carcinogenesis.