Optimizing PD-L1 evaluation on cytological samples from advanced non-small-cell lung cancer

Area of Science:

• Oncology
• Molecular Pathology
• Cancer Diagnostics

Background:

• Programmed cell death-ligand 1 (PD-L1) expression is a key biomarker for predicting response to immune checkpoint inhibitors in non-small-cell lung cancer (NSCLC).
• Advanced NSCLC diagnosis often relies on minimally invasive procedures yielding small biopsies or cytological samples, posing challenges for comprehensive biomarker assessment.

Purpose of the Study:

• To evaluate the feasibility and reliability of assessing PD-L1 protein and gene status on direct cytological smears from NSCLC patients.
• To compare PD-L1 assessment on cytological samples with paired histological samples.

Main Methods:

• PD-L1 expression was analyzed using immunocytochemistry (ICC) and immunohistochemistry (IHC) on cytological smears and histological samples, respectively.
• PD-L1 gene status was determined by fluorescence in situ hybridization (FISH) on both sample types.
• The study included 52 advanced NSCLC patients with paired cytological and histological samples.

Main Results:

• PD-L1 overexpression was detected in 17% of cytological samples and 13.5% of matched biopsies.
• High concordance (92.3%) was observed between ICC and IHC for PD-L1 protein assessment.
• Concordance for PD-L1 gene status between cytology and histology was 69.2%, with no correlation found between IHC and FISH results.

Conclusions:

• PD-L1 protein and gene assessment on direct cytological smears is feasible and reliable for NSCLC patients.
• Cytological samples can serve as a viable alternative for PD-L1 testing when histological samples are inadequate.
• This approach supports timely treatment decisions for NSCLC patients undergoing immune checkpoint inhibitor therapy.