PD-L1 expression in small cell and non-small cell lung carcinomas and its relationship with prognosis

Lung cancers are the leading cancer-related deaths worldwide and their survival rates are very low. Therefore, it is important to search for new treatment methods in these patient groups. A treatment option that targets immune checkpoints and is called immunotherapy has been widely used in cancer treatment. Anti-PD-L1 drugs are most common immunotherapy regimenes. Tumor cells bind to PD-L1 on their cell surface and PD-1 region on T lymphocytes and inactivate them. Inactivated T lymphocytes cannot destroy tumor cells. Anti-PD-L1 drugs eliminate the inactivity on immune cells and ensure the destruction of tumor cells again. Today, anti-PD-L1 drugs are frequently used in non-small cell lung carcinomas (NSCLC). Immunotherapy is a new treatment option in extensive stage small cell carcinomas (SCLCs), which are poorly differentiated neuroendocrine tumors. Large cell neuroendocrine carcinoma (LCNEC) is in the high-grade neuroendocrine tumor group of the lung like SCLC. In addition to chemotherapy (CT) options, targeted therapies are increasingly used in LCNECs. In our study, we investigated PD-L1 expression in tumor and immune cells in a total of 255 cases, 117 NSCLC, 107 SCLC and 31 LCNEC. PD-L1 expression was detected lower in SCLC than NSCLCs. There was no significant difference in PD-L1 expression between LCNEC and NSCLC, and between LCNEC and SCLC. Although the rate of PD-L1 expression in tumor cells in SCCs is very low, survival was found to be significantly higher in cases with PD-L1 expression in immune cells. It was also found that as the severity of PD-L1 expression in immune cells increased in SCLCs, life expectancy increased significantly. There was no significant difference was found between PD-L1 expression and life expectancy in NSCLC and LCNEC. The relationship between PD-L1 expression and survival, which has been found in many studies in NSCLCs, was not seen in this study because of our cases consisted of metastatic patiens. Accordingly, it was thought that the evaluation of PD-L1 expression in immune cells in SCLCs would provide information in terms of life span of the cases.