Aligning digital CD8⁺scoring and targeted next-generation sequencing with programmed death ligand 1 expression: a pragmatic approach in early-stage squamous cell lung carcinoma

Aims To study programmed death ligand 1 ( PD ‐L1) expression, tumour‐infiltrating T lymphocytes ( TIL s) and the molecular context in patients with early‐stage squamous cell lung carcinomas ( SCC s). Methods and results The study included samples from 40 patients (discovery cohort) and 29 patients (validation cohort) diagnosed with early‐stage SCC . PD ‐L1 immunohistochemistry ( IHC ) was performed with three commercially available clones (E1L3N, SP 263 and SP 142). CD 8 + TIL s were scored with a digital algorithm. All tumours were analysed with targeted next‐generation sequencing ( NGS ). Additionally, TP 53 mutations were investigated with direct sequencing. In both cohorts, we observed a significant association between CD 8 + TIL s density and high PD ‐L1 IHC expression in tumour cells ( TC s). Furthermore, high SP 142 PD ‐L1 expression in immune cells ( IC s) was also associated significantly with CD 8 + TIL s density. Therefore, CD 8 + TIL s density discriminated between patients with high versus low PD ‐L1 IHC expression with excellent sensitivity and specificity. Interestingly, the highest percentages of PD ‐L1‐positive TC s with the three antibodies were found in samples with cyclin‐dependent kinase 6 ( CDK 6 ) amplification, with high amplification of proto‐oncogene C‐Myc ( CMYC ) or with cyclin D1– PI 3 kinase subunit alpha ( CCND 1– PIK 3 CA ) co‐amplification. High SP 142 PD ‐L1 IHC expression in IC s showed a non‐significant correlation with TP 53 mutations. Conversely, most cases with fibroblast growth factor receptor 1 ( FGFR 1 ) amplification were negative for all PD ‐L1 clones. Conclusions Our preliminary results support the use of digital CD 8 + TIL s scoring and targeted NGS alongside PD ‐L1 expression. The approach presented herein could help define patients with SCC s candidates to immune checkpoints inhibitors.