Differences in PD-L1 Expression between oral and oropharyngeal squamous cell carcinoma

Treatment of metastasized or recurrent oral (OSCC) and oropharyngeal (OPSCC) squamous cell carcinoma remains challenging. Targeted antibody-based therapy inter alia for PD-1 / PD-L1 axis shows promising results, but whether PD-L1 expression varies between the subentities remains unclear. The expression pattern of PD-L1 (EPR19759 antibody, Abcam, Berlin, Germany) and p16 (CINtech® Histology Kit, Ventana, Oro Valley, USA) was determined immunohistochemically and analyzed by HALO™ Image Analysis Software (Indica Lab, Albuquerque, USA). For PD-L1, combined positivity score (CPS), tumor proportion score (TPS) and histoscore, were assessed and results correlated with epidemiological data. In total, 161 patients (OSCC: n = 78, OPSCC: n = 83) were included. A mean of 43.6% (±34.0%) of the specimen showed increased PD-L1 expression that did not differ quantitatively between subentities (TPS: p = 0.159, CPS: p = 0.078), but qualitatively (histoscore: p = 0.003). In the mean follow-up period (45.6 months), contrary to age (p = 0.006) and advanced T-Status (p = 0.018), PD-L1 expression did not correlate with overall (OS, p = 0.191) and recurrence free survival (RFS: p = 0.193) in both subentities. No correlation of p16 and PD-L1 expression was found (p = 0.844). PD-L1 is differentially expressed between OSCC and OPSCC, however without influence on OS. Furthermore, p16 status was not related to PD-L1 expression. This may have implications for future (immune) therapeutical approaches for oral cancer.