DNA methylation, the addition of methyl groups to the cytosine residues of DNA, is a form of epigenetic modification that mainly occurs in CpG islands usually present in promoter regions.8 Abnormal hypermethylation of certain CpG islands may lead to transcriptional silencing and inactivation of cancer suppressor genes.9 In recent years, several studies have reported the application of circulating free DNA biomarkers in CRC diagnosis and screening.6, 10 The SEPT9 gene belongs to a class of GTPases involved in numerous cellular processes. This evidence concerns the gene SEPTIN9 and colorectal carcinoma.