Abstract 3673: Socioeconomic disparities and the genomic landscape of gastric cancer
Authors: Zanabria Daniel , Galvez-Nino Marco , Cho Cristina Eunbee , Fajardo Williams , Saravia Luis , Araujo Jhajaira , Alfaro Alejandro , Quispe Lidia , Cornejo Melanie , Medina Paula , Carbajal Junior , Montenegro Paola , Zevallos Alejandra , Aguilar Alfredo , Pinto Joseph A. 
Published: June 2022

Abstract
Background: Gastric cancer is a malignancy of diverse etiology and exposition to risk factors may vary in distinct socioeconomic (SE) groups. Our aim was to compare the landscape of genomic alterations in malignant gastric tumors between different socioeconomic groups in Peru.
Methods: We conducted a preliminary prospective study in one private clinic and two public hospitals in Lima and Ica (Peru). We evaluated 20 patients with gastric carcinomas, 10 of which were classified as low SE status (LSE) and 10 as medium/high SE status (MHSE), according to the Peruvian Association of Market Intelligence Companies (APEIM) classification system. We conducted a comprehensive genomic profiling of gastric tumors with the FoundationOne CDx platform. We compared rates of alterations in single nucleotide variants, copy number variations, tumor mutation burden, microsatellite instability, and pathways altered.
Results: In our cohort, the mean age at diagnosis was 67.5 yo vs 61 yo, while 40% vs 55.6% were male patients, for LSE vs MHSE, respectively. We found alterations in driver genes in 19 patients (10 LSE and 9 MHSE). Histological analysis of the tumor samples revealed a higher proportion of intestinal histology in the LSE group (80%) compared to MHSE (55.6%). On the other hand, the diffuse subtype pattern was more prevalent in the MHSE group (33%) compared to LSE (20%). One case of mixed histology was observed in the high SE group. Both LSE and HMSE showed a similar distribution of Bormann Classification/type, where most of the samples were of class III/IV (75%) followed by class I/II (25%). Furthermore, genomic profiling analysis showed 45 driver alterations in LSE, while only 25 alterations were detected in MHSE. the most frequently altered genes were TP53 and KRAS in both SE groups, but with a higher incidence in LSE (60% and 20%, respectively). Components of the MAPK pathway were altered in 50% vs 33.3%, while the DNA repair pathway was altered in 20% vs 11%, in LSE vs MHSE, respectively. The PI3K/Akt pathway was altered in only one case of LSE. Median of tumor mutation burden was 6.1Mut/Mb in LSE vs 5.3Mut/Mb MHSE. Only one case with microsatellite instability was found in LSE.
Conclusions: Despite the limitations of this preliminary study, we observed some differences in the genomic background between patients from different socioeconomic groups. Therefore, the need of a thorough diagnosis approach that leads to the use of a comprehensive treatment that includes targeted therapy and immunotherapy could be different based on the SE status of the patient. Further research on this topic will be necessary.
Citation Format: Daniel Zanabria, Marco Galvez-Nino, Cristina Eunbee Cho, Williams Fajardo, Luis Saravia, Jhajaira Araujo, Alejandro Alfaro, Lidia Quispe, Melanie Cornejo, Paula Medina, Junior Carbajal, Paola Montenegro, Alejandra Zevallos, Alfredo Aguilar, Joseph A. Pinto. Socioeconomic disparities and the genomic landscape of gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3673.