Conclusions:

This is the largest study to investigate the distinct molecular landscape of pts with different PD-L1 expression levels in GE cancers. • TMB and the proportion of MSI-H/dMMR were only significantly increased in patients with CPS-H, while no significant difference was seen between CPS-L and M in the overall analysis. • Our data may provide novel insights for pt selection (e.g. pts with gene mutations involved in epigenetic modification) and the development of rational combination immunotherapy (e.g. drugs targeting MAPK pathway) in GE cancers.