Incidence and Prognostic Significance of PD-L1 Expression in High-Grade Salivary Gland Carcinoma

Objective PD-L1 is one of the predictors of immunotherapy efficacy. Our goal was to analyze its expression and prognostic significance in high-grade salivary gland carcinoma (SGC). Methods PD-L1 expression was evaluated using paraffin-embedded specimens from patients with surgically treated high-grade SGC, and it was scored by the tumor proportion score (TPS), combined positive score (CPS), and immune cell (IC) score. Associations between clinicopathological variables, disease-free survival (DFS), overall survival (OS) and PD-L1 expression were assessed. Results TPS >= 1% occurred in 47 patients with an incidence of 43.1%, and it was significantly related to an advanced tumor stage. In patients with TPS < 1%, TPS ranging from 1% to 20%, and TPS >= 20%, the 5-year DFS rates were 36%, 26%, and 13%, respectively, and the difference was significant. In patients with TPS < 1%, TPS ranging from 1% to 20%, and TPS >= 20%, the 5-year OS rates were 49%, 24%, and 13%, respectively, and the difference was significant. CPS >= 1 occurred in 87 patients with an incidence of 79.8%. IC scores of 0, 1, 2, and 3 were noted in 24 (22.0%), 37 (33.9%), 31 (28.4%), and 17 (15.6%) patients, respectively. Both CPS and IC scores had no impact on DFS or OS. Conclusions The expression of PD-L1 in tumor cells of high-grade SGCs was not uncommon, and it was significantly associated with tumor stage. PD-L1 expression in tumor cells rather than in immune cells indicated a poor prognosis.

Automated summary

The expression of PD-L1 in high-grade salivary gland carcinomas was significantly associated with tumor stage, and a tumor proportion score (TPS) of >= 1% was common in 43.1% of patients, with significant differences in 5-year disease-free survival and overall survival rates.