Cytotoxic T Lymphocyte Density and PD-L1 Expression Predict the Response to Anti-PD1 Therapy in Recurrent Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common head and neck cancers, and immunotherapy targeting programmed cell death 1 (PD-1) has become a treatment option for recurrent OSCC after surgery and radiation therapy. However, few studies have identified definitive biomarkers for predicting patient response to anti-PD1 therapy in OSCC. In the present study, biopsy specimens were obtained from 23 patients with recurrent OSCC who were subsequently treated with anti-PD1 therapy. Immunohistochemical examinations of CD3, CD8, FOXP3, CD103, CD163, programmed cell death ligand 1 (PD-L1), HLA-A/B/C, HLA-DR, and β2 microglobulin were performed, and their correlation with clinical response was statistically analyzed. We found that an increased density of CD8-positive lymphocytes and increased PD-L1 expression predicted a favorable response to anti-PD1 therapy in recurrent OSCC. In contrast, clinical factors such as age and sex, and immune-related factors such as HLA-Classes I and II, were not associated with the response to anti-PD1 therapy. Taken together, our results suggest that immunohistochemical analysis of CD8 and PD-L1 may be useful for predicting the efficacy of anti-PD1 therapy in recurrent OSCC.