P33.02 Comparison of PD-L1 Protein Expression Between Primary and Metastatic Lesions in Lung Cancer Patients

PD-L1 expression assessed by IHC is the central companion diagnostic test for immunotherapy. However, most trials have not stipulated the tissue source used to assess expression. Here we assess PD-L1 expression as performed in the “real world” to determine if sampling sites, histologic subtypes, genders and age groups affect the likelihood of high-level expression.