Expression of Programmed Cell Death Ligand 1 Protein and Other Biomarkers in Patients with Gastric Cancer and Gastroesophageal Junction Cancer: A Retrospective Single Centre Study in Brazil

Jessica Gonçalves Azevedo^1*Beatriz de Araújo Cortez¹Maria Aparecida do Carmo Rego¹Felipe Berlinski¹Dominihemberg Ferreira¹Angelica Carreira Dos Santos²Ana Beatriz Machado de Almeida²Paula de Mendonça Batista¹Cicera Pimenta Marcelino^1*Fernanda Franco Munari^3,4Iara Viana Vidigal Santana⁴Vinicius Duval Da Silva⁴Guilherme Ribeiro⁴Gustavo Noriz Berardinelli⁵Diego Burgardt⁶Durval Wohnrath⁶Rui Manuel Reis^5,6,7,8

• ¹MSD Brazil, São Paulo, Brazil
• ²IQVIA Brazil, São Paulo, Brazil
• ³Molecular Oncology Research Center, Barretos Cancer Hospital, Barretos - São Paulo, Brazil
• ⁴Department of Pathology, Barretos Cancer Hospital, Barretos - São Paulo, Brazil
• ⁵Molecular Diagnostic Laboratory, Barretos Cancer Hospital, Barretos - São Paulo, Brazil
• ⁶Department of Upper Digestive Surgery, Barretos Cancer Hospital, Barretos - São Paulo, Brazil
• ⁷Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal
• ⁸Molecular Oncology Research Center, Barretos Cancer Hospital, Barretos, Barretos - São Paulo, Brazil

Background: Programmed cell death ligand 1 (PD-L1) is a key prognostic biomarker that can predict response to immunotherapies in patients with gastric cancer (GC) and gastroesophageal junction cancer (GEJC). However, there is a lack of real-world data on the distribution of PD-L1 and other prognostic biomarkers among patients with GC and GEJC in Brazil. Objectives: To analyze PD-L1 expression, the microsatellite instability (MSI) and human epidermal growth factor receptor 2 (HER-2) status among patients with GC and GEJC in a Brazilian cancer hospital and to evaluate the association between PD-L1 expression and other biomarkers and clinicopathological parameters. Methods: This observational, retrospective study was conducted between March 2019 and May 2019 at the Barretos Cancer Hospital in Brazil. The levels of PD-L1 expression and other biomarkers were analyzed for patients whose formalin-fixed paraffin-embedded tumor tissue samples were preserved at the hospital. PD-L1 expression was measured by the immunohistochemical (IHC) method. MSI was determined by molecular assays, whereas IHC and fluorescence in situ hybridization (FISH) assays were conducted to evaluate HER 2 expression. The association between PD-L1 expression, MSI, HER-2-positivity, and clinicopathological parameters was determined using a chi-square test. Results: A total of 162 patients were included in the study. Most of the patients were male (65.4%), with a mean age of 61 years. PD-L1 expression (CPS ≥1) was observed in 49.4% of patients (n = 80) of patients, whereas MSI-high and HER-2 expression were reported in 12.3% (n = 20) and 8.0% (n = 13), respectively. PD L1 expression was significantly associated with older age and MSI. Conclusion: A high prevalence of PD-L1 expression was observed among patients with GC and GEJC, but HER-2-positivity was lower than global prevalence. PD-L1 expression was associated with MSI-high status. The study outcomes can be used for the selection of appropriate therapies for patients with GC and GEJC in Brazil.