Immunohistochemistry‑quantified EGFR mutant protein expression percentage outperforms next‑generation sequencing‑derived mutational abundance for predicting tyrosine kinase inhibitor efficacy in non‑small cell lung cancer

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are the standard first-line therapy for EGFR-mutant non-small cell lung cancer (NSCLC), yet treatment efficacy varies widely among patients.The aim of the present study was to investigate the correlation between immunohistochemistry (IHC)-quantified EGFR mutant protein expression percentage (MPEP) in tumour tissue and EGFR-TKI efficacy, as well as the clinical predictive value of this mutation percentage.The present retrospective study included 50 patients with NSCLC with EGFR exon 19 deletion or leucine-to-arginine substitution at codon 858 mutations who received EGFR-TKI treatment.IHC was performed to quantify the percentage of EGFR-mutant tumour cells, and the association between this mutation percentage and progression-free survival (PFS), overall survival (OS) and objective response rate (ORR) was analysed.The median IHC-MPEP was 51.18%, with an overall ORR of 50% in the cohort.Receiver operating characteristic curve analysis identified 52.66% as the optimal cut-off value for efficacy prediction.Patients in the high mutation percentage group (≥52.66%;n=24) had a significantly longer median PFS (21.0 vs. 8.5 months; P<0.05) and OS (30 vs. 18 months; P=0.023), as well as a higher ORR (70.8 vs. 30.7%;P= 0.004), compared with the low mutation percentage group.The EGFR mutation percentage was confirmed as an independent prognostic factor for PFS (hazard ratio= 0.946; 95% confidence interval, 0.927-0.966;P<0.001).Therefore, IHC-MPEP is a reliable quantitative method that can effectively predict EGFR-TKI efficacy and survival benefit in patients with EGFR-mutant NSCLC. Immunohistochemistry-quantified EGFR mutant protein expression percentage outperforms next-generation sequencing-derived mutational abundance for predicting tyrosine kinase inhibitor efficacy in non-small cell lung cancer