Immunohistochemistry (IHC) staining of PD-L1

Eleven tissue biopsies of this study were performed IHC staining of PD-L1 expression with 22C3 anti-PD-L1 antibody (Dako) according to the protocol reported previously ¹⁷. PD-L1 IHC was evaluated by a pathologist based on the tumor proportion score (TPS) with membranous and/or cytoplasmic staining, and divided into three groups: no-expression (<1% of tumor cells), low expression (1%-49%) and high expression (≥50%).