Cell-blocks are suitable material for programmed cell death ligand-1 immunohistochemistry: Comparison of cell-blocks and matched surgical resection specimens in lung cancer.

objectiveProgrammed cell death ligand-1 (PD-L1) has emerged as a predictive biomarker in lung cancer. PD-L1 immunohistochemistry (IHC) assay predicts the response to immunotherapy, but cytology specimens are often the only samples available in a considerable proportion of advanced lung cancer patients. We delineate practical feasibility and efficacy of cytology cell-block (CB) specimens for PD-L1 expression and concordance between cytology CBs and surgical resection specimens.

methodsIn total, 58 eligible patients with primary lung cancer who received computed tomography-guided percutaneous needle aspiration and surgery were included. PD-L1 IHC (clone SP263) was performed on CBs prepared from residual liquid-based cytology material and matched surgical resection specimens. PD-L1 positive tumour cell proportion was categorised in four score groups: (a) <1%; (b) ≤1% to <10%; (c) ≤10% to <50%, (d) ≥50%.

resultsComparison of PD-L1 expression in cytology CBs and matched surgical resection specimens showed a high concordance (κ value 0.65). According to the therapeutic guideline of immunotherapeutic agents, a positive percent agreement was 94.34%, and a negative percent agreement was 100% at a cut-off value for positivity of 1% PD-L1 expression. There was a significant difference observed with regard to rates of PD-L1 positivity when comparing smoking history (P = 0.02), age (P = 0.04) and pathological TNM stage (P = 0.04).

conclusionsThe results show that cytology CBs evaluated for PD-L1 IHC assay have high concordance with matched surgical resection specimens and can be used for assessing PD-L1 expression. Also, we propose that CBs are suitable materials for evaluating PD-L1 expression while simultaneously performing both diagnostic and molecular tests.