Tumor biopsies and immunohistochemistry
tumor
CPS, TUMOR, POSITIVE
Prior to the administration of sintilimab, tumor biopsies were collected from the subjects. These biopsies could be either archival samples or freshly obtained. Immunohistochemistry (IHC) staining was conducted on formalin-fixed paraffin-embedded (FFPE) tumor tissue samples to identify the presence of PD-L1 (using DACO, 22C3) and CD8 + T cells (using Abcam, C8/144B, ab17147). The IHC staining process adhered to the recommended protocols provided by the respective manufacturers. Two certified pathologists evaluated PD-L1 expression on tumor cells by examining stained tissue samples.Regarding the 22C3 antibody, PD-L1 expression was assessed using two scoring systems: the Combined Positive Score (CPS) and the TPS. The CPS was calculated by taking the number of PD-L1-stained cells, which includes tumor cells, lymphocytes, and macrophages, and dividing it by the total count of viable tumor cells. The resulting quotient was then multiplied by 100. The TPS, however, represented the proportion of viable tumor cells exhibiting partial or complete membrane staining at any intensity. The calculation methodology for CPS and TPS can be found in 