O18: AN EXPLORATION OF THE GENOME OF MUCINOUS ADENOCARCINOMA OF THE RECTUM

Abstract Introduction Mucinous adenocarcinoma (MA) of the rectum accounts for 5-15% rectal cancers. This histological subtype has been shown to have a worse response chemoradiotherapy and long term outcomes when compared non-mucinous (NMA). The aim this study was compare genomic landscape MA NMA. Method Using BGISEQ PE100 platform, paired end whole genome sequencing carried out on tumour matched normal tissue from cases MA. Cancer Genome Atlas interrogated identify further NMA with data that could be used as control group. In-depth bioinformatic analysis undertaken landscapes two subtypes were compared. Result A total 14 74 microsatellite instability-high rate in group 14.29% vs 4.05% POLE mutations found 5.41% 0.00% KRAS, BRAF PIK3CA more frequent whereas TP53 APC common Significant differences between groups identified most frequently mutated genes. Copy number alteration, mutational signatures, structural variation microbiome findings will also described. Conclusion is not just phenotypically distinct, it distinct genotype. implications considering neoadjuvant adjuvant treatment strategies future. Take-home message differs perspective may future