2.5. Immunohistochemistry assay

Archived tumor samples obtained prior to toripalimab treatment were used for PD‐L1 and CD8 double immunohistochemistry staining by a rabbit anti‐human PD‐L1 antibody (1:800;SP142, spring bioscience, California,USA) and mouse anti‐human CD8 antibody (1:30;CA1817T, Biorad, California, USA). PD‐L1 expression on the membrane of both tumor cells and tumor‐infiltrating immune cells was assessed by 2 certified pathologists. A positive PD‐L1 expression was defined as ≥5% membrane staining of any intensity on tumor cells or tumor‐infiltrating immune cells. Positive CD8 staining was defined as “++” or above by pathologists.