CD274 and prostate carcinoma: A highly variable frequency of PD-L1 expression has been reported in the included studies measuring the expression of PD-L1 in prostate cancer, which ranged from 7.7 to 82.4% (Ebelt et al., 2009; Gevensleben et al., 2016a; Calagua et al., 2017; Haffner et al., 2018), and the pooled frequency of PD-L1 is 35%.