ERBB2 gene as a potential therapeutic target in small bowel adenocarcinoma

Aim of the study: Small bowel adenocarcinoma (SBA) is a rare and aggressive tumour with poor outcomes. Because of its low incidence, the number prospective studies remains insufficient leading to poor knowledge and absence of standard of care. Aiming to better understand small bowel carcinogenesis we investigated the frequency of somatic muta- tions in a large data set of patients in more than 740 mutational hotspots among 46 genes. Methods: In total, 83 SBA cases were selected from two European databases. The sequencing was performed using the Ion 316 Chip. Additionally we looked into ERBB2 expression and microsatellite instability (MSI) status. Results: The tumours most frequently were duodenal (47%) and stage P3 (63%). Eight genes were mutated with a frequency >5%: KRAS, TP53, APC, SMAD4, PIK3CA, ERBB2, BRAF and FBXW7. ERBB2 alterations are present in 10 patients (12%) through mutations (7 cases) or amplifications (3 cases). ERBB2 mutations were significantly associated with duodenal tumour location (P = 0.04). In this group, there was a positive association with dMMR status (P = 0.006) and APC mutation (P = 0.02) but negative association with p53 mutations (P = 0.038).