Dako automated link 48 platform

We consecutively collected 54 patients with pathologically confirmed adenocarcinoma of lung and activating EGFR mutation at diagnosis between January 2016 and December 2017 from Seoul St. Mary’s Hospital, Incheon St. Mary’s Hospital, Bucheon St. Mary’s Hospital, St. Paul’s Hospital, and Uijeongbu St. Mary’s Hospital, Korea. Based on pack-year (PY) defined as average number of cigarettes per day/20× years of smoking, patients were categorized as never smokers (<100 cigarettes in their life-time), light smokers (0< PY <30), or heavy smokers (PY ≥30). Genotying of EGFR was done using peptide nucleic acid (PNA)-mediated PCR clamping method such as PNAClamp TM EGFR Mutation Detection Kit (PANAGENE, Inc., Daejeon, Korea) using real-time PCR. Activating EGFR mutation was defined as exon 19 deletion or exon 21 point mutation. PD-L1 immunohistochemistry testing was performing using PD-L1 clone 22C3 pharmDx kit and Dako automated Link 48 platform (Dako, Carpenteria, CA, USA). PD-L1 tumor proportion score (TPS) was calculated as the percentage of at least 100 viable tumor cells with complete or partial membrane staining.

For each tumor sample, the histological subtype of carcinomatous components (adenocarcinoma, squamous cell carcinoma, and large-cell carcinoma) and sarcomatoid components were collected.
To measure the PD-L1 expression, we used the PD-L1 clone 22C3 pharmDx kit and Dako Automated Link 48 platform (Dako, Carpenteria, USA), which is clinically used for the evaluation of the PD-L1 expression in NSCLC at our institution. The PD-L1 expression was calculated as the percentage of complete or partial membrane staining in a section that included at least 100 viable tumor cells. Necrotic areas were excluded from scoring. A high expression of PD-L1 was defined as ≥50% staining of tumor cell membrane, and PD-L1 negative was defined as <1% staining.