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.