Comparative Study of Mutations in Single Nucleotide Polymorphism Loci of KRAS and BRAF Genes in Patients Who Underwent Screening Colonoscopy, With and Without Premalignant Intestinal Polyps

Aim: Our aim was to perform a comparison study of the mutation rate of V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), and v-Raf murine sarcoma viral oncogene homolog-B (BRAF) genes between blood-based cell-free DNA (cfDNA), and tissue sample biopsies in individuals undergoing screening colonoscopy. Materials and Methods: All specimens were collected from January 2015 to January 2016. A total of 92 blood samples and colonic biopsy specimens were collected from healthy individuals with no polyps undergoing screening colonoscopy (group A, n=35), patients with colorectal cancer (group B, n=27), and patients with neoplastic intestinal polyps (group C, n=30). Peripheral blood was collected from each patient and a focal tissue biopsy was conducted. Results: We only found a limited statistically significant difference (p=0.046) in the mutation analysis for codon 12 of the KRAS gene when we compared tissue biopsies from patients in group B to those from group C. In the blood samples, only the rate of mutation in codon 12 of the KRAS gene in samples of group B was significantly higher than that in group A (p=0.013). Conclusion: Blood cfDNA may be a promising tool in CRC screening as it may discriminate patients with CRC compared to healthy individuals and those with colonic polyps, even though it does not appear useful in predicting the presence of colonic polyps.