[Prognostic significance of PD-L1 expression as a potential predictor of survival in gastric cancer].

Background: Currently, PD-L1 expression in patients with tumors of various localizations is being actively studied. Studies on the expression of PD-L1 detected by clones SP142 and SP263 in gastric cancer (for the drugs atezolizumab and durvalumab, respectively) are rare in the literature. The prognostic role of PD-L1 expression in patients who were not treated with immune checkpoint inhibitors has also not been investigated.

Objective: To determine the expression level of PD-L1 (clones SP263 and SP142, Roche Ventana) in gastric cancer specimens and evaluate its effect on overall survival in patients who did not receive adjuvant therapy with immune checkpoint inhibitors.

Material And Methods: The study included 131 patients with a verified diagnosis of gastric cancer. The material obtained from 127 patients was stained with antibodies to PD-L1 SP263, and from 126 patients - with antibodies to PD-L1 SP142. A multivariate Cox regression model with Wald's step-by-step exclusion algorithm was used to evaluate predictors of survival.

Results: The total five-year survival rate of patients in the PD-L1-negative tumor group was significantly lower than the total five-year survival rate of patients in the PD-L1-positive tumor group, which was 50.0% and 40.0% also for both clones (=0.027). An increase in the expression of PD-L1 clone SP263, determined by both the CPS and TPS method, reduces the chances of death by 1.35 times (=0.02) and 1.61 times (=0.004), respectively. An increase in the expression of PD-L1 clone SP142, determined by the CPS method, reduces the chances of death by 1.54 times (=0.005).

Conclusion: The survival rate of patients in the group of PD-L1-positive tumors is significantly higher than in patients in the group of PD-L1-negative tumors. Elevated PD-L1 expression, as assessed by the SP263 and SP142 clones, is an important prognostic marker that predicts a higher chance of overall survival for patients, even though these patients are not receiving immune checkpoint inhibitors adjuvant therapy.