Programmed death-ligand 1 expression in tumor cells and tumor-infiltrating lymphocytes are associated with depth of tumor invasion in penile cancer

The present study aimed to demonstrate the proportion of the programmed death-ligand 1 (PD-L1) expression in penile cancer patients and the association with clinicopathological parameters. Formalin-fixed paraffin-embedded specimens were obtained from 43 patients with primary penile squamous cell carcinoma treated at Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, between 2008 and 2018. PD-L1 expression was evaluated by the immunohistochemistry using an SP263 monoclonal antibody. PD-L1 positivity was defined as >25% tumor cell staining or >25% tumor-associated immune cell staining. The correlation between PD-L1 expression and clinicopathological parameters was analyzed. A total of eight of 43 patients (18.6%) were identified as positive for PD-L1 expression in tumor cells and tumor-infiltrating lymphocytes. In the PD-L1 positive group, there was a significant association with pathological T stage (P=0.014) with a higher percentage of PD-L1 positive tumors in T1 stage compared with T2-T4 stage. In this cohort, there was a trend towards longer survival in patients with positive PD-L1 expression (5-year OS: 75% vs. 61.2%, P=0.19). Lymph node involvement and the location of tumor at the shaft of penis were two independent prognostic factors for survival. In conclusion, the PD-L1 expression was detected in 18% of penile cancer patients and high expression of PD-L1 was associated with the early T stage.