Evaluation of stool melting curve analysis of methylated CpG island promoters as an alternative for early noninvasive diagnosis of colorectal tumors

e15036 Background: Previous studies have shown that assessment of promoter hypermethylation of a limited number of genes in tumor biopsies may identify all colorectal tumors analyzed. The aim of the present study was to assess the clinical usefulness of a panel of methylation biomarkers in stool DNA in the diagnosis of colorectal tumors using Methylation Curve (MC) analyses, a technique that simultaneously analyze all CpG residues within a promoter. Methods: Promoter methylation status of 5 tumor-related genes (RARB2, p16 INK4a , MGMT, p14 ARF and APC) was analyzed in DNA stool samples and corresponding tissues in an initial set of 12 newly diagnosed patients with primary colorectal carcinomas and 20 with colorectal adenomas using Methylation-specific PCR (MSP). Results were validated in a set of 88 patients (20 healthy subjects, 17 inflammatory bowel disease, 23 adenomas, 28 carcinomas) using MC analyses. Median age for every group was 63, 51, 66 and 67 y respectively. Results: In the initial set, the majority [10 of 12 (83%) carcinomas and 18 of 20 (90%) adenomas] of biopsies were positive for at least one marker. In stool DNA prevalence was 75% for carcinomas (9 of 12) and 60% for adenomas (12 of 20) with no false positive in stools. In the validation set MC was used. Analytical sensitivity of MC was 5% of methylated alleles for p16 INK4a , p14 ARF , RARB2 and APC and 10% for MGMT. In the validation set MC analyses of biopsies showed that at least one marker was positive in 22 of 28 (79%) carcinomas and 16 of 23 (70%) adenomas. In stool DNA, these percentages were 64% (18 of 28) for carcinomas and 42% (9 of 23) for adenomas. No aberrant methylation was observed in healthy subjects and in 2 of 15 (13%) of IBD patients aberrant RARB2 methylation was detected. Conclusions: Melting Curve analysis of a panel of methylation markers in stool DNA is a good alternative for the early non-invasive diagnosis of colorectal tumors. [Table: see text]