PO-382 Differentially methylated sites in histologically negative surgical margins of oral squamous cell carcinoma patients

Abstract

Introduction Oral squamous cell carcinoma (OSCC) is the most common malignant tumour of the head and neck. The presence of microscopic tumour in surgical margins contributes to increased local recurrence rates and decreased overall survival. However, from 10% to 30% of patients with negative histological margins present locoregional recurrences. Many studies have suggested the presence of epigenetic changes prior to the onset cancer phenotype in the mucosa adjacent to the primary tumour. Thus, the aim of this study was to evaluate the hypermethylation profile of negative surgical margins from patients with OSCC as a prognostic factor for tumour recurrence. Material and methods The methylation profile of 32 cryopreserved histologically negative surgical margins samples was performed using the Illumina Infinium MethylationEPIC BeadChip platform. The patients were divided into the following two groups: a) 16 who developed local recurrence and b) 16 who did not developed local recurrence. The generated data were analysed with RStudio software using the ChAMP (Chip Analysis Methylation Pipeline) package. Results and discussions The majority of patients were male (68.8%), had initial disease (71.9%) and were tobacco users (71%). All samples presented less than 1% of failed probes, so they were all included in the subsequent analyses. Probes that anneal at more than one site in the genome, probes with Single Nucleotide Polymorphisms (SNPs) and/or failed in more than one sample were excluded, leaving 7 80 437 probes for comparison. In the comparative analysis between the groups, 908 CpG sites differentially methylated were identified using p Conclusion Our results demonstrated that patients with negative histological margins have a differentially methylated signature, which is important for the identification of individuals at high risk of developing local recurrence of OSCC, decreasing morbidity and improving survival rates.