Abstract 2184: Gene characteristics of Chinese patients with small bowel cancer

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Abstract Background: Small bowel cancer is a rare malignancy which account for only 1-3% of all malignant gastrointestinal tumors. Herein, we aim to provide an overview of gene characteristics of Chinese patients with small bowel cancer based on the location of the tumor in the small bowel. Methods: Tumor samples of 324 Chinese patients with small bowel cancer were consecutively collected in China from February 2018 to May 2020, among them, 289 patients with cancer located in duodenum (group 1), 35 patients with cancer located in the other region of small bowel (group 2). Next generation sequencing (NGS) was performed to detect gene mutation, microsatellite instability (MSI), and tumor mutational burden (TMB) measured by a 733 gene panel by 3D Medicines, a laboratory accredited by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). Results: NGS results revealed that the main mutated genes were different between two groups, in detail, the top ten gene mutation in group 1 were TP53 (51.4%,18/35), KRAS (45.7%, 16/35), APC (34.3%, 12/35), POLE (20.0%,7/35), PIK3CA/POLD1/MSH2 (17.1%,6/35), mTOR/PRSS1/LPR1B/BRCA1/SMAD4 (14.3%,5/35). While top ten gene mutation in group 2 were TP53 (66.4%,192/289), KRAS (49.8%, 144/289), ERCC1 (38.8%, 112/289), UGT1A1 (31.5%, 91/289), APC (29.4%, 85/289), BRCA1 (28.7%,83/289), AKT2 (27.3%, 79/289).In addition, TMB level and percentage of MSI-H were also compared between the two groups. 12 patients were available for TMB analysis in group 1, 59 for group 2, the average TMB level in two groups were 23.84 mutants/Mb and 7.8 mutants/Mb, respectively. 50%(6/12) and 11.8%(7/59) were under 10 mutants/Mb in two groups. What's more, the percentage of MSI-H in two groups were 16.7% (5/30) and 3.2% (8/243). Conclusion: Patients with cancer located in duodenum patients with cancer located in the other region of small bowel displayed obvious difference in gene landscape, this imply that these patients should be treated differently. Citation Format: Quan Zhao, Hushan Zhang, Zhuyun Lei, Jianing Sheng, Dun Xiong. Gene characteristics of Chinese patients with small bowel cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2184.

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