PD-L1 Expression in Men with Penile Cancer and its Association with Clinical Outcomes

Abstract

BackgroundIt has been hypothesized that PD-L1 expression in tumor cells and tumor-infiltrating immune (TII) cells may contribute to tumor progression by inhibiting antitumor immunity. ObjectiveTo investigate the association between PD-L1 expression in tumor cells and TII cells and clinical outcomes in penile cancer. Design, setting, and participantsA cohort of 222 men treated for penile squamous cell carcinoma (SqCC) at Örebro University Hospital between 1984 and 2008 with long-term follow-up (median 34 mo) was evaluated for PD-L1 expression in tumor cells and TII cells via immunohistochemistry. Outcome measurements and statistical analysisAssociation between clinicopathological features and PD-L1 expression was estimated using χ2 and Fisher's exact tests. For survival analyses, Kaplan-Meier curves with log-rank tests and multivariate Cox proportional hazards regression models were used. Results and limitationsWe found that 32.1% of the tumors and 64.2% of the TII cells expressed PD-L1. Our data demonstrate that penile SqCC patients with PD-L1–positive tumor cells or TII cells are at significant risk of lower cancer-specific survival and that the prognostic value of PD-L1 expression was strongest for tumor cell positivity. The use of tissue microarrays rather than whole sections may be viewed as a limitation. ConclusionsTumor PD-L1 expression independently identifies penile SqCC patients at risk of poor clinical outcomes. Patient summaryWe investigated how many patients with penile cancer had tumors that manufactured PD-L1, a protein that decreases the ability of the immune system to fight cancer. We found that up to one-third of penile tumors make this protein. Patients whose tumors make PD-L1 have more aggressive penile cancer and worse clinical outcomes.