EGFR Mutation Testing

All the EGFR tests were performed using the tumor tissues. Genomic DNA was extracted from formalin-fixed, paraffin-embedded, 5-µm-thick tissue sections using the High Pure Template Preparation Kit (Roche Applied Science, Mannheim, Germany). The extracted DNA was stored at −20°C until analysis. EGFR Pyro Kit (QIAGEN Korea Ltd., Seoul, Korea) and PyroMark Q24 System (QIAGEN Korea Ltd., Seoul, Korea) were used to detect EGFR mutations by real-time polymerization chain reaction (PCR). The primer sets covered mutations or deletions spanning exons 18 to 21 of the genes encoding the tyrosine kinase domain of EGFR. The results were interpreted according to the manufacturer’s instructions.