Clinicopathological characteristics of RHOA mutations in a Central European gastric cancer cohort

Genomically stable gastric cancers (GCs) are enriched for the diffuse phenotype and hotspot mutations of RHOA. Here we aimed to validate the occurrence, phenotype and clinicopathological characteristics of RHOA mutant GCs in an independent Central European GC cohort consisting of 415 patients. The RHOA genotype (exon 2 and 3) was correlated with various genotypic, phenotypic and clinicopathological patient characteristics. Sixteen (3.9%) tumours had a RHOA mutation including four hitherto unreported mutations, that is, p.G17Efs*24, p.V24F, p.T37A and p.L69R. RHOA mutation was more prevalent in women (5.4% vs 2.8%), distal GCs (4.5% vs 2.4%), in poorly differentiated GCs (G3/G4; 4.8% vs 1.1%), T1/T2 tumours (6.2% vs 3.1%) and lacked distant metastases. Nine RHOA mutant GCs had a diffuse, four an intestinal, two an unclassified and one a mixed Laurén phenotype. KRAS and RHOA mutations were mutually exclusive. A single case showed both a RHOA and a PIK3CA mutation. No significant difference was found in the overall survival between RHOA mutant and wildtype GCs. Our study confirms the occurrence and clinicopathological characteristics of RHOA hotspot mutations in an independent patient cohort. However, we found no evidence for a prognostic or growth advantageous effect of RHOA mutations in GC.