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MA 06 - Lung Cancer Biology I (ID 660)
- Event: WCLC 2017
- Type: Mini Oral
- Track: Biology/Pathology
- Presentations: 1
MA 06.02 - Cytology and Surgical Pathology Specimens are Comparable Testing Substrates for PD-L1 Immunohistochemistry in Lung Cancer (ID 9063)
15:45 - 17:30 | Author(s): V. Torous
Immunohistochemical (IHC) testing for programmed death ligand 1 (PD-L1) expression by non-small cell lung cancer (NSCLC) specimens has become standard of care to help select immune checkpoint inhibitor therapy. The companion IHC assay for pembrolizumab has been validated and approved for use on surgical pathology specimens; however, the performance of this assay when applied to cytology specimens is not well characterized.
Following IRB approval, all NSCLC cytology or surgical pathology specimens obtained from 11/2015 to 5/2017 at our institution that were tested for PD-L1 expression by a commercial vendor (Integrated Oncology/LabCorp, NY) using the FDA-approved companion diagnostic PD-L1 clone 22C3 pharmDx kit on the Dako Automated Link 48 platform (Dako, Carpenteria, CA) were identified. Patient cohorts where testing was performed on diagnostic cytology vs. surgical pathology specimens were compared. Tumor PD-L1 expression was stratified by clinically relevant groups: <1%, 1-49%, and ≥50%. Tumor genotyping results for EGFR, KRAS, ALK, and ROS1 were also collected.
Cytology formalin-fixed paraffin-embedded (FFPE) cell blocks included endobronchial ultrasound transbronchial needle aspirates (57%), pleural/pericardial fluids (28%), fine needle aspirates (13%), and bronchial washings/lavages (2%). Surgical FFPE specimens included small core/incisional biopsies (60%), bronchial biopsies (12%), and large resections (28%). PD-L1 testing was successful for over 96% (223/232) of specimens (Table). Overall, EGFR mutations were more frequent with no/low PD-L1 expression, ALK rearrangements with high PD-L1 expression, but no relationship between KRAS mutations and PD-L1 expression.
PD-L1 Tumor Proportion Score Stratified by Specimen TypeChi-squared value=2.95, p>0.39 (not significant); TPS=tumor proportion score
Cytology Cell Block Surgical Pathology <1% PD-L1 TPS 35 (37.2%) 52 (37.7%) 1-49% PD-L1 TPS 20 (21.3%) 35 (25.4%) ≥50% PD-L1 TPS 33 (35.1%) 48 (34.8%) Failed Analysis 6 (6.4%) 3 (2.2%) Total 94 (100%) 138 (100%)
For NSCLC, no statistically significant differences in PD-L1 expression patterns were observed between cytology cell block and surgical pathology specimens, implying that in clinical practice any adequate cytology cell block or surgical pathology specimen could be utilized for testing. Importantly, analysis of clinical outcomes with use of first line pembrolizumab based on cytology vs surgical pathology specimen PD-L1 ≥50% expression is currently ongoing.
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