Comparison of PD-L1 and VISTA level in primary and recurrent/refractory tissue after therapy in head and neck cancers

Expression of PD-L1 and VISTA has been demonstrated in a variety of tumors including head and neck cancers. PD-L1 and VISTA are thought to play a role in escape from the immune system, tumor progression and treatment response in tumoral tissue which are responsible for the development of immune tolerance, immune elimination and inflammation in normal tissues. These molecules are seen as a potential marker in predicting treatment response and situating immune checkpoint inhibitors in treatment. In this study, it was aimed to investigate the effects of radiotherapy and chemoradiotherapy on PD-L1 and VISTA expression. A total of 47 patients with larynx, oral cavity and hypopharynx cancer were included in the study. In this study, PD-L1 and VISTA expressions were compared between the primary biopsy at the time of diagnosis and refractory tissue biopsies of patients who received definitive chemoradiotherapy or recurrent tissue biopsies of patients who received surgery with adjuvant radiotherapy/ chemoradiotherapy. Biopsy specimens were examined immunohistochemically. Expression of PD-L1 was evaluated by TPS and VISTA expression was evaluated by IC. The results of our study showed that PD-L1 and VISTA expression levels did not change with radiotherapy/ chemoradiotherapy in head and neck cancers (PD-L1 p=0,542; VISTA p=0,425). First biospy PD-L1 and VISTA expression was found to be significantly higher in clinical lymph node positive patients compared to node negative patients (PD-L1 p=0,038; VISTA p=0,018). Positive correlation was found between PD-L1 and VISTA expression (p<0,001; r=0,560). No statistically significant correlation was found between PD-L1 and VISTA expression of first biopsy and disease-free survival (PD-L1 p=0,568; VISTA p=0,842). There was no relation between PD-L1 expression of first and second biopsy and overall survival (first biopsy PD-L1 p=0,725; second biopsy PD-L1 p=0,443). The overall survival of patients with VISTA expression above 1% on the first biopsy was found to be significantly shorter than those with less than 1% (P=0.048). No significant relation was seen between second biopsy VISTA expression and overall survival (p=0,212). As a result, it was shown that PD-L1 and VISTA expression did not change with radiotherapy or chemoradiotherapy. A clear demonstration of the immune response which is generated by radiotherapy and chemotherapy is critical for the positioning of immunotherapy in treatment. Further studies are needed to evaluate the relationship between PD-L1 and VISTA expression with radiotherapy and chemoradiotherapy.