Histopathological correlation of PDL-1 and its effect on prognosis in patients with oral cavity squamous cell carcinoma

Oral cavity malignancies are highly morbid and mortal, with more than 90% consisting of squamous cell carcinomas (SCC). PD-L1 protein, found on the membrane of tumor cells, binds to T lymphocytes and inactivates them. PD-L1 expression has been shown to be associated with survival in many malignancies, especially malignant melanoma, colorectal carcinoma and lung cancer. The aim of our study is to evaluate the relationship of PD-L1 expression with patient characteristics and survival outcomes in oral cavity SCCs. For this purpose, adult patients diagnosed with oral cavity SCC who applied to Hacettepe University Faculty of Medicine, Department of Otorhinolaryngology between 2014 and 2022 were included in the study. Baseline demographic and clinical data of the patients were examined retrospectively. Paraffin blocks containing the primary tumor and lymph node metastases in the pathology archive were evaluated by immunohistochemistry for PD-L1 expression, and tumor proportion score (TPS) and combined positive score (CPS) were obtained. Possible relationships between TPS and CPS and patient characteristics and survival outcomes were investigated using statistical methods. The mean age of a total of 96 patients included in the study (61.5% male and 38.5% female) was 58.7±15.5 years. The frequency of CPS ≥ 20% in patients diagnosed with lower lip SCC was found to be significantly higher compared to other localizations (85.7% vs. 60.3%, p = 0.015). Similarly, TPS positivity was associated with lower lip involvement (≥ 1%, p=0.014; ≥ 20%, p<0.001). In univariate analyses, tongue or lower lip involvement, stage III-IV disease or ECOG-PS ≥2 at diagnosis, receiving chemotherapy or radiotherapy, and ≥20% TPS in the primary tumor tissue were associated with progression-free survival (PFS). The multivariate regression model showed that ECOG-PS ≥2 was an independent factor determining the risk of progression (HR: 2.206, 95% CI: 1.153-4.219, p=0.017). When the model was applied to 37 patients who had not received chemotherapy or radiotherapy, ECOG-PS ≥2 (HR: 26.39, 95% CI: 4.089-170.4, p<0.001), stage III-IV disease at diagnosis (HR: 10.57, 95% CI: 1.874-59.66, p=0.008) and ≥ 20% TPS in primary tumor tissue (HR: 0.125, 95% CI: 0.026-0.594, p=0.009) were determined as independent risk factors for PFS. In conclusion, our study revealed that increased tumoral PD-L1 expression is an independent factor that reduces the risk of progression in early stage patients who have not received chemotherapy or radiotherapy.