Revisiting the Role of PD-L1 Overexpression in Prognosis and Clinicopathological Features in Patients with Oral Squamous Cell Carcinoma.

Simple Summary: The implications of PD-L1 expression in oral squamous cell carcinoma (OSCC) remain unclear. Most published series and systematic reviews suffer from cohort heterogeneity and the use of different immunohistochemical tools, leading to controversial and non-conclusive results without significant clinical relevance. A retrospective monocentric study, including all patients with OSCC diagnosed and treated between January 2020 and May 2022, was performed. The method used to measure PD-L1 was reliable and accurate, with a correlation coefficient between PD-L1 expression in a biopsy and a surgical piece of 0.83 (p < 0.0001). PD-L1 expression was observed in large tumors (p < 0.001) and was correlated with the presence of lymph node metastases (p < 0.004). This study aimed to assess the immunohistochemical expression of PD-L1 in squamous cell carcinomas of the oral cavity with a reliable and accurate method and its possible associations with different histopathological, clinical, and prognostic variables in a patient cohort with OSCC from a single institution. Background: PD1 and its ligand PD-L1 are related to prognosis in many solid tumors; however, their role in oral squamous cell carcinoma (OSCC) remains unclear. Methods: A retrospective monocentric study including all patients with OSCC diagnosed and treated between January 2020 and May 2022 was performed. PD-L1 expression was assessed per a combined positive score (CPS), considering a CPS of > or equal to 1 as positive (1–20 indicating "low expression" and ≥20 indicating "high"). A descriptive analysis of the patient cohort and tumors was performed, including tumor size, stage, lymph node involvement, recurrence, and survival. Results: In total, 65 patients (65 tumors) were analyzed. A total of 66.15% of the tumors were in advanced stages (III-IV), of which 97.67% expressed PD-L1+, compared with 71.42% in the early stages (I–II). T4 tumors expressed PD-L1 in 100% of cases, compared with 54% in T1 tumors. A total of 50.79% of the tumors showed lymph node involvement (pN+), with 100% of the pN+ showing PD-L1+. The prevalence of pN+ was 59.38% vs. 40.63% for high vs. low PD-L1 expression, respectively. Patients' follow-ups ranged from 2 to 34.5 months. No significant difference was seen between overall survival (OS) and PD-L1 +/− (CPS ≥ 1 vs. CPS < 1) or high (CPS ≥ 20) and low (CPS < 20) PD-L1 expression (p < 0.97 and 0.64, respectively). Conclusions: The method used to measure PD-L1 (a laboratory test with Dako 22C3 anti-PD-L1 primary antibodies) was reliable and accurate, with a correlation coefficient between PD-L1 expression in the biopsy and the surgical piece of 0.83 (p < 0.0001). A CPS of ≥1 was observed in large tumors (p < 0.001) and was correlated with that of lymph node metastases (p < 0.004). Further analysis of PD-L1 expression in OSCC and studies to determine its relevance in tumor biology and prognosis is needed. [ABSTRACT FROM AUTHOR]