Abstract 1536: Tumor heterogeneity and primary versus metastatic evaluation of PD-L1

Immunotherapy with checkpoint inhibitors allowing recovery of effector cell function, has been demonstrated to be highly effective in many tumor types and represents a true revolution in oncology. However, current assays for the prognostic and/or predictive role of tumor PD-L1 expression are not fully standardized with respect to either quantity or distribution of expression, or regarding the concordance of expression in primary tumor versus metastasis. To assess tumor heterogeneity, we evaluated PD-L1 expression using the Ventana SP-263 assay in paired formalin fixed paraffin embedded (FFPE) blocks from the same primary tumor for each of 22 lung squamous cell carcinoma (SCC), 6 lung adenocarcinoma (ADC), 53 gastric ADC, 55 colorectal ADC, 60 urothelial bladder carcinoma, 3 pancreatic ductal ADC and 4 head and neck SCC. In addition, PD-L1 expression in primary tumor and synchronous metastasis was evaluated in 32 cases of lung neoplasm (10 ADC +22 SCC), 30 cases of gastric adenocarcinoma, 55 cases of colorectal adenocarcinoma, and 16 head and neck SCC, each with corresponding synchronous metastases. PD-L1 expression was determined by pathologist evaluation of the percentage of positive tumor cells and cases were grouped into categories representing Citation Format: Lorenzo Colarossi, Eleonora Aiello, Marie Cumberbatch, Cristina Colarossi, Chris Womack, Lorenzo Memeo. Tumor heterogeneity and primary versus metastatic evaluation of PD-L1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1536.