PD-L1 and p16 Expression in Penile Squamous Cell Carcinoma From an Endemic Region

Penile squamous cell carcinoma (PSCC) is a rare malignancy with higher incidence in developing countries. Treatment options include surgery, radiation therapy, and systemic chemotherapy. However, effective treatments for advanced disease are lacking. To understand the biology underlying PSCC may help the development of new therapeutic strategies. The objective of this study was to evaluate immunohistochemical expression of programmed death-ligand 1 (PD-L1) and p16 in PSCC and its association with clinicopathologic features and outcomes.

A cohort of 40 patients with PSCC from an academic institution in Brazil was analyzed. Clinicopathologic features and outcomes were retrospectively collected. PD-L1 and p16 immunohistochemical expression were performed in formalin-fixed paraffin-embedded specimens. PD-L1 was positive with any staining in more than 1% of tumor, and p16 was positive in more than 10%. Associations were performed using the Mann-Whitney and Fisher exact test. Kaplan-Meier curves were used to estimate survival rates with log-rank.

Of 35 patients, 5 were excluded, 4 owing to a lack of data and 1 owing to no tumor available; 18 (51.4%) patients were PD-L1-positive (PD-L1⁺). PD-L1⁺ was associated with larger tumors (P = .027). There was an association between PD-L1⁺ and p16 expression (P = .002). PD-L1⁺ was more frequent in grade II and III disease than grade I (77.8% vs. 22.2%) and was expressed in all patients with grade III disease. Lymph node involvement was associated with PD-L1 expression (69.2% PD-L1⁺ vs. 30.8% PD-L1-negative). The 5-year mortality was 37.1%.

PD-L1 expression appears to be associated with p16 expression, larger tumors, and worse clinical outcomes in PSCC and may provide clinical data for new studies to evaluate anti-PD-L1 immune therapies.