Clinicopathological and Prognostic Significance of MSI Status and PD-L1 Expression in Turkish Patients with Gastric Cancer

The aim of study was to evaluate the prognostic role of MSI status and PD-L1 expression in gastric cancer and the relationship of these parameters with clinicopathological features. Eighty-six gastric cancer patients who underwent surgical resection were analysed. MSI status and PD-L1 expression in tumour samples were evaluated by immunohistochemistry (IHC). PD-L1 IHC was scored using the combined positive score (CPS). Survival analysis was conducted using the Kaplan-Meier method. The rate of PD-L1 expression in tumour cells was 34.9% (n=30), and the frequency of PD-L1 expression in immune cells with a CPS >= 1% was 57% (n=49). MSI-high (MSI-H) was detected in 11.6% (n=10) of cases and was more common among PD-L1-positive cases (p=0.021). MSI-H status was significantly correlated with older age, larger tumours, positive PD-L1 expression, and the adenocarcinoma subtype. PD-L1 expression was associated with lymph node metastasis, the adenocarcinoma subtype, MSI, preoperative treatment and an improved response to preoperative chemotherapy. In our study, the impact of MSI status on survival was not demonstrated, but positive PD-L1 expression (>= 1%) in tumour cells (15.7 vs. 53.4 months. p=0.008)and in immune cells (20.4 vs. not reached (NR); p=0.027) was associated with decreased overall survival. PD-L1 expression is related to a poor prognosis in patients with gastric cancer.