Abstract
Different immunohistochemical (IHC) assays were approved for PD-L1 expression examination on tumor cells in qualification to immune-checkpoint inhibitors therapy in NSCLC patients. These assays have some similarities, but also very serious differences. We assessed 2 IHC tests for PD-L1 expression evaluation in NSCLC tumors with different pathological diagnoses and genetic abnormalities.We enrolled 48 NSCLC patients (median age: 65 years) with known status of EGFR and ALK genes. We compared the effectiveness of PD-L1 expression examination of two IHC assays with 22C3 (Dako) and SP142 antibodies (Ventana). IHC tests were performed in resected tissue samples and in cellblocks from bronchoscopy biopsies (formalin-fixed paraffin-embedded). IHC staining was carried out on Dako Autostainer Link 48 and Ventana Benchmark GX.The percentage of tumors with PD-L1 expression of ≥5% and ≥50% on tumor cells was significantly (p<0.05) higher in assay with 22C3 (66.7% and 45.8%) than with SP142 antibody (39.6% and 22.9%). The median percentage of tumor cells with PD-L1 expression was significantly (p<0.0001) higher in test with 22C3 than with SP142 antibody. Percentage of squamous cell carcinoma (SCC) patients with PD-L1 expression was significantly higher than of non-SCC patients. Large group of patients without PD-L1 expression on tumor cells was identified among patients with common EGFR mutations and ALK rearrangement.Our results support that the highest PD-L1 expression on tumor cells occurs in SCC patients and in adenocarcinoma patients without common, druggable genetic abnormalities. The above mentioned results were clearly visible in IHC assay with 22C3 (strong cell staining).
Highlights
Immunotherapies have been successfully used in the treatment of various neoplasms, including melanoma and non-small cell lung cancer (NSCLC)
The percentage of tumors with PD-L1 expression on ≥1% of tumor cells was slightly higher in IHC reaction with 22C3 (72.9%) than with SP142 antibody (60.4%)
The median percentage of tumor cells with PD-L1 expression detected by 22C3 antibody was significantly (p
Summary
Immunotherapies have been successfully used in the treatment of various neoplasms, including melanoma and non-small cell lung cancer (NSCLC). Three PD-1 (programmed death 1) or PD-L1 (programmed death ligand 1) inhibitors are approved in USA and/or in Europe for treatment of NSCLC patients. Nivolumab – a monoclonal anti-PD-1 antibody, is approved for advanced NSCLC patients after failure of first-line therapy. Pembrolizumab (monoclonal antibody against PD-1) can be used in advanced NSCLC patients in second- (tumor must contain at least 1% of PD-L1-positive tumor cells) or in first-line therapy (tumor must contain at least 50% of PD-L1-positive tumor cells). Atezolizumab is the first anti-PD-L1 antibody which was approved for patients with advanced NSCLC after failure of first-line therapy. The association between effectiveness of anti-PD-1/anti-PD-L1 inhibitors and tumoral PD-L1 expression evaluated by immunohistochemistry (IHC) assays has been reported in clinical trials. Three different IHC assays, along with their corresponding drugs, were approved [1,2,3,4,5,6,7]
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