O18: AN EXPLORATION OF THE GENOME OF MUCINOUS ADENOCARCINOMA OF THE RECTUM. (27th April 2021)

• Record Type: Journal Article
• Authors: Reynolds, IS; O'Connell, E; Fichtner, M; McNamara, DA; Kay, EW; Prehn, JHM; Furney, SJ; Burke, JP
• Is Part Of: British journal of surgery. Volume 108(2021)Supplement 1
• Publication Date: 2021-04-27
• Subjects: Surgery -- Periodicals; 617.005
• DOI: 10.1093/bjs/znab117.018
• Languages: English
• ISSNs: 0007-1323

Abstract

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