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

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.