Relationship Between EGFR Mutation Status and Clinicopathological Parameters in Non-Small Cell Lung Carcinomas and Correlation of PD-L1 Expression

Background and Objectives: In this study, we investigate clinical and pathological parameters that may be associated with EGFR mutations. We aimed to contribute to the literature by understanding other potential clinical and pathological factors that could be useful in predicting patients with a high probability of responding to immunotherapy and by investigating the relationship between PD-L1 expression and driver mutations. Materials and Methods: This study included 141 biopsy specimens and 97 resection specimens diagnosed with NSCLC between 2015 and 2022. Statistical analyses were performed using the IBM SPSS Version 29.0 program. Results: In our study, consistent with the literature, a significant association was found between the presence of EGFR mutations and female sex and non-smoking status (p < 0.001). No statistically significant association was found between PD-L1 expression status and individual driver alterations, including EGFR, BRAF, ALK, and ROS1 (p > 0.05 for all). The association between PD-L1 expression status and non-adenocarcinoma histological types, particularly squamous cell carcinoma (10.1%) and NSCLC-NOS (14.5%), was statistically significant; PD-L1 positivity was higher in non-adenocarcinoma tumors (70.6%) compared to adenocarcinomas (43.3%; p = 0.009). Conclusions: In groups of patients with early-stage and locally advanced disease, the mean overall survival time was significantly lower for those with ALK translocations, which contrasts with the existing literature, and this finding was determined to be an independent poor prognostic factor (HR: 8.6, 95% CI: 1.9–38, p = 0.004).