What is the clinical utility of the Combined Positive Score (CPS) for PDL-1 expression when considering pembrolizumab for gastric cancer?

From multiple studies, it is very clear that higher staining for PDL-1 on tumors and immune cells (combined expression, resulting in the CPS (combined positive score)) is correlated with increased Response Rate, PFS and clinical benefit of anti-PD1 drugs. Pembrolizumab is approved for gastric cancer...