Exploratory analysis
tumor, PD-L1-positive tumor
CPS, TUMOR
Pretreatment tumor biopsy was obtained using EUS for biomarker analysis, including programmed cell death-ligand 1 (PD-L1) expression, tumor mutational burden (TMB), and tumor immune microenvironment (TIME). PD-L1 expression was assessed using the PD-L1 IHC 22C3 pharmDx assay (Agilent Technologies). The combined positive score (CPS) was used to define PD-L1 expression, which was determined by dividing the number of PD-L1-positive tumor and immune cells by the total number of viable tumor cells and multiplying by 100. Next-generation sequencing (NGS) was performed using whole-exome sequencing or a 733-gene panel (3D Medicines Inc.). As defined, the TMB was the number of somatic single nucleotide variations (SNVs) and insertions/deletions (indels) per megabase of coding genome sequenced. Synonymous and non-synonymous mutations, stop gains/losses, and splicing variants were all considered SNVs. Indels included both frameshift and non-frameshift insertions and deletions. Non-coding alterations were excluded from the calculation of TMB. TIME was evaluated using multiplex immunofluorescence (mIF) staining. The quantities of CD8