Prognostic significance of PD-L1 expression and CD8(+) TILs density for disease-free survival in surgically resected lung squamous cell carcinoma: a retrospective study

BACKGROUND: This study sought to depict the genomic landscape of patients with surgically resected lung squamous cell carcinoma (LUSC) and its relationship with clinical outcome indicators. METHODS: We retrospectively collected the clinical data of 180 patients from the electronic medical records and applied targeted sequencing and immunohistochemistry (IHC) to depict the genomic landscape, including the tumor mutation burden (TMB), programmed cell death-ligand 1 (PD-L1), and cluster of differentiation CD8(+) tumor-infiltrating lymphocytes (CD8(+) TILs). And comparative analysis and survival analysis of these parameters were conducted to find prognostic factors for clinical outcome. RESULTS: PD-L1+ tumor cells were observed in 75 (41.7%) of the patients, the median rate of CD8(+) TILs was 11.5 [4, 24], and the median TMB was 9.4 (7.5–13.7) mutations per megabase (mut/Mb). Patched receptor 1 (PTCH1) gene mutation frequency was significantly associated with CD8(+) TILs density (12% vs. 1%; P=0.024). High PD-L1 expression and CD8(+) TILs+ were significantly associated with longer disease-free survival (DFS), and a further subgroup analysis revealed that both were significantly correlated with the DFS of stage I/II patients but not stage III patients. CONCLUSIONS: The results suggest that only PTCH1 gene mutation frequency was correlated with CD8(+) TILs density. Additionally, intense CD8(+) TILs density and high PD-L1 expression were found to be associated with longer DFS. Our findings provide insights into the precise treatment strategy for surgically resected LUSC patients.