<jats:title>Abstract</jats:title>
<jats:p>Objective: Incidence and mortality rates of gastric cancer (GC) are characterized by their geographical heterogeneity. In Chile, GC is the leading cause of cancer death. To date, GC patients' response to standard therapies remains limited. A molecular classification of GCs may deliver better stratifications. Herein, we obtained clinical data, protein expression and genetic profiles in a cohort of Chilean patients and present a molecular classification that correlated with overall survival (OS) rates.</jats:p>
<jats:p>Methods: A total of 71 patients were included. Clinical data were obtained from medical records; protein expression was analyzed by a Tissue MicroArray. We also performed Next Generation Sequencing to assess p53 status (WT or Mut). Supervised clustering was used to generate a molecular classification. Kaplan-Meier method was used to calculate OS. Hazard ratio was calculated by Cox regression.</jats:p>
<jats:p>Results: We defined 5 GC subgroups: Epstein-Barr virus+ (EBV, n=9; 13%), Microsatellite Instable (MSI, n=9; 13%), E-cadherin loss (EMT-like, n=12; 17%). The remaining patients (those MSS-/EBV-/not EMT-like) were classified either as p53 WT (n=21; 30%) or p53 Mutated (n=20; 28%). According to subgroups, 5-year survival rates were: MSI=77,8%; EBV=43.2%; p53WT=43.5%; p53Mut=25% and EMT-like=16.7%. Hazard ratios for p53Mut and EMT-like were 5.1 (IC 95%: 1.16-22.41; p=0.031) and 6.81 (IC 95%: 1.48-31.24; p=0.014), respectively against the MSI group used as reference. This association is maintained in a multivariate model using age, gender and stage.</jats:p>
<jats:p>Conclusions: Our study defined 5 GC subgroups. These are associated to OS rates. EMT-like and p53Mut subgroups displayed poorer survival. Future studies should explore actionable targets in these subsets in order to improve their survival.</jats:p>
<jats:p>Citation Format: Mauricio P. Pinto, Matias Muñoz-Medel, Miguel Cordova-Delgado, Ignacio N. Retamal, Gareth Owen, Maria Loreto Bravo, Ricardo Armisen, Marcelo Garrido. A molecular classification of gastric cancer in Chilean patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5293.</jats:p>
