Reproducibility of the EGFR immunohistochemistry scores for tumor samples from patients with advanced non-small cell lung cancer

Abstract

Epidermal growth factor receptor (EGFR) is overexpressed in >60% of non-small cell lung cancer (NSCLC) cases. In combination with radiotherapy or chemotherapy, first-line treatments with antibodies against EGFR, including cetuximab and necitumumab, have demonstrated benefits by increasing overall survival (OS), particularly in patients who overexpress EGFR. The present study evaluated the interobserver agreement among three senior pathologists, who were blinded to the clinical outcomes and assessed tumor samples from 85 patients with NSCLC using the H-score method. EGFR immunohistochemistry was performed using a qualitative immunohistochemical kit. The reported (mean ± standard deviation) H-scores from each pathologist were 111±102, 127±103 and 128.53±104.03. The patients with average H-scores ≥1, ≥100, ≥200 and between 250-300 were 85.9, 54.1, 28.2 and 12.9, respectively. Patients who had an average H-score >100 had a shorter OS time compared with those with lower scores. Furthermore, patients with EGFR mutations who were treated with EGFR-tyrosine kinase inhibitors (TKIs) and had an average H-score >100 had a longer OS time compared with those with an average H-score <100. The interobserver concordance for the total H-scores were 0.982, 0.980 and 0.988, and for a positive H-score ≥200, the interobserver concordance was 0.773, 0.710 and 0.675, respectively. The determination of EGFR expression by the H-score method is highly reproducible among pathologists and is a prognostic factor associated with a poor OS in all patients. Additionally, the results of the present study suggest that patients with EGFR mutations that are treated with EGFR-TKIs and present with a high H-score have a longer OS time.

Keywords: H-score; biomarkers; cetuximab; epidermal growth factor receptor; immunohistochemistry; necitumumab; non-small cell lung cancer; tumor.

Figure 1.

Representative examples of positive and negative immunohistochemical staining for EGFR. Membrane staining was scored as follows: (A) 3+ for dark staining of the linear membrane visible at a magnification of ×100; (B) 2+ for intermediate staining visible at a magnification of ×400; (C) 1+ for light staining only visible at a magnification of ×400; and (D) 0 for no staining visible at a magnification of ×400. EGFR, epidermal growth factor receptor.

Figure 2.

Kaplan-Meier curves by epidermal growth factor receptor score (<200 vs. ≥200). OS, overall survival; CI, confidence interval.

Figure 3.

Kaplan-Meier curves by epidermal growth factor receptor score (<100 vs. ≥100). OS, overall survival; CI, confidence interval.