Gastric adenocarcinoma classification: Association with clinicopathological features and overall survival in Moroccan patients

Background The Cancer Genome Atlas (TCGA) project and Asian Cancer Research Group (ACRG) recently categorized gastric cancer (GC) into molecular subtypes. Unfortunately, these classification systems require high cost and sophisticated molecular technologies, consequently preventing their widespread use in routine diagnostic practice. In the present study, we have used less expensive and widely available techniques in molecular classification of gastric adenocarcinomas. Methods This is a retrospective study of ninety-seven patients with gastric adenocarcinomas diagnosed at Hassan II University Hospital in Fez between January 2014 and September 2018. All cases were classified into five subgroups using immunohistochemistry, in situ hybridization, and multiplex PCR, based on a panel of four markers (Epstein-Barr virus, Microsatellite instability, E-cadherin and p53). Epstein-Barr virus infection was detected by EBER-ISH (Epstein-Barr encoding RNAs- in situ hybridization). Microsatellite instability evaluation was performed by multiplex PCR using a panel of five quasimonomorphic mononucleotide repeat markers (NR27, NR21, NR24, BAT25, and BAT26). E-cadherin and p53 expressions were evaluated by immunohistochemistry using ventana anti-E-cadherin (36) Mouse Monoclonal Primary Antibody (ready to use) and flex monoclonal mouse anti-human p53 protein (clone DO-7, Dako; ready to use), respectively. Results All cases were classified into five subgroups: Epstein–Barr virus positive tumours (n=6; 6.2%), microsatellite instability tumours (n=13; 13.4%), tumours with aberrant E-cadherin expression (n=28; 28.8%), tumours with aberrant p53 expression (n=31; 32%), and tumours with normal p53 expression (n=19; 19.6%). Epstein-Barr virus-positive tumours were predominantly poorly differentiated (66.7%) and were found exclusively in male patients (100%). Microsatellite instability tumours were characterized by a predominance of Lauren’s intestinal histology (84.6%). Tumours with aberrant E-cadherin expression were diagnosed in younger patients (mean age, 56 years) and exhibited mostly the Lauren’s diffuse/mixed histology (60.7%). Tumours with p53 aberrant expression were well/moderately differentiated in 83.9% of the cases and had a history of tobacco smoking in 32.3% of the cases. Tumours with p53 normal expression were more frequent in elderly patients (mean age, 65 years). Survival analysis showed that microsatellite instability tumours had the best overall survival, followed by normal p53 expression tumours, aberrant p53 tumours, aberrant E-cadherin expression tumours and Epstein-Barr virus positive tumours (log rank test, P < 0.001). Conclusions This study shows that gastric adenocarcinomas can be classified into biologically and clinically different subgroups using techniques available in routine diagnosis. This simplified classification system can be employed as not only a surrogate for molecular classification, but also for predicting the prognosis of GC patients. Legal entity responsible for the study The authors. Funding This research is part of a thesis project on gastric cancer, funded by the Faculty of Medicine and Pharmacy of Fez (FMPF) and Hassan II University Hospital of fez, through Sidi Mohamed Ben Abdellah University, under the scope of the call for research projects 2017/2018. Barretos Cancer Hospital's internal funds partially supported this study. This work has been funded by National funds, through the Foundation for Science and Technology (FCT) - project UIDB/50026/2020 and UIDP/50026/2020; and by the projects NORTE-01-0145-FEDER-000013 and NORTE-01-0145-FEDER-000023, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). MVP was supported by the Fundação para a Ciência e Tecnologia (FCT), within the scope of scientific employment. SPC was a recipient of an FCT Ph.D. fellowship (2020.05779.BD). NJP was recipient of UMove(ME) Erasmus ICM, KA107 project 2018 fellowship at Universidade do Minho, Braga, Portugal. Disclosure E. Van Cutsem: Advisory / Consultancy: Array, Astellas, AstraZeneca, Bayer, Beigene, Biocartis, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Daiichi, Halozyme, GSK, Incyte, Ipsen, Lilly, Merck Sharp & Dohme, Merck KGaA, Novartis, Pierre Fabre, Roche, Servier, Sirtex, Taiho; Research grant / Funding (institution): Amgen, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Ipsen, Lilly, Merck Sharp & Dohme, Merck KGaA, Novartis, Roche, Servier. All other authors have declared no conflicts of interest.