Abstract 694: the Chilean Gastric Cancer Task Force: an Update of Results

Abstract Background: Gastric cancer (GC) is the world's second leading cause of cancer death. Gene alterations, treatment responses and mortality rates are geographically heterogeneous. In Chile, GC is the leading cause of cancer death. It affects 17.6/100,000 people and causes >3,000 deaths per year. Therapy response and clinical outcomes are highly heterogeneous and thus a better patient stratification may improve patient outcomes. The Gastric Cancer Task Force (GCTF) is a Chilean collaborative, non-interventional, non-concurrent, prospective study that seeks to stratify gastric adenocarcinomas (GACs) using clinical data, genomic and protein alterations in a cohort of 200 patients. Methods: A total of ~100 patients were included in this preliminary analysis. Five different Single Nucleotide Polymorphisms (SNP) for the MTHFR and DPYD genes were assessed using genomic DNA. Tissue Microarray (TMA) analysis included: p53, p16, HER2, PDL1, MSI, and EBV. The analysis also included 120 clinical parameters for these patients. Results: Preliminary results show that 63.6% (n=100) of patients were male. A 38% of patients were stage I-II, 39.55% were stage III, and 22.3% were stage IV. Tumor location was predominantly at the stomach body (48.5%), a 30% of patients had comorbidities and 50% had a cancer family history. Median overall survival (OS) was 29.0 months. In stage IV patients, median OS was 14.0 months. Regarding TMA data a 26% were PDL1+, 13% were EBV+, MSI was present in 13% of patients, 38% were p16+, a 48% had a mutated p53 and 9.0% were HER2+++. Finally, one out of the 4 DPYD SNPs was present in all analyzed patients (100%). Using a multivariate Cox-regression model we found that PDL1+ patients had a 15-fold increase in the risk of death. In contrast, EBV+ patients had a significant reduction in their risk of death. Both were adjusted by sex, age & TNM. Conclusion. Our preliminary data suggest an elevated proportion of EBV+ among GC patients in the Chilean population compared to similar studies in other geographical regions. On the other hand, majority of patients are males and classified as stage III/IV, which is in-line with previous reports in South America. Finally, PDL1+ and EBV+ correlate with an increase and a reduction in the risk of death, respectively. ClinicalTrials.gov identifier: NCT03158571, Registered May 18th, 2017 Citation Format: Erica C. Koch, Mauricio P. Pinto, Ignacio N. Retamal, Maria L. Bravo, Maria J. Maturana, Miguel Cordova-Delgado, Diego Romero, Nathaly De La Jara, Javiera Torres, Manuel Espinoza, Carlos Balmaceda, Matias Freire, Valentina Garate-Calderon, Ricardo Avila, Fernando Crovari, Alejandro H. Corvalan, Ricardo Armisen, Gareth I. Owen, Marcelo Garrido. The Chilean Gastric Cancer Task Force: An update of results [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 694.