ERBB2 gene as a potential therapeutic target in small bowel adenocarcinoma.

205 Background: Small bowel adenocarcinoma (SBA) is an aggressive tumor responsible for poor outcomes with an expected median OS at 5 years inferior to 30%. Because of its low incidence, few prospective studies have been performed leading to insufficient knowledge and absence of standard of care. Aiming to better understand the small bowel carcinogenesis process we screened for somatic mutations a large data set of patients in more than 740 mutational hotspots among 46 genes. Methods: In total, 83 SBA cases were selected from 2 European databases. The sequencing was performed using the Ion 316 Chip. We additionally looked into MSI status and ERBB2 expression (immunochemistry and FISH). Results: Tumors were mostly located in the duodenum (47%) and stage ≥ 3 (63%). Among the 46 genes investigated, 8 were mutated in more than 5% of the cases: KRAS, TP53, APC, SMAD4, PIK3CA, ERBB2, BRAF, and FBXW7. Compelling mutations (7 cases) and amplifications (3 cases) 12% of the patients had an ERBB2 alteration. In this...