A total of 26 publications were excluded for the following reasons: inclusion of peritoneal mesothelioma (n = 9), inappropriate study design (n = 8), outcomes not reported by PD-L1 expression (n = 4), population untested for PD-L1 expression using IHC (n = 4), and no outcomes of interest reported (n = 1). The gene discussed is CD274; the disease is peritoneal mesothelioma.