Immunohistochemistry for EGFR Mutation Detection in Non-Small-Cell Lung Cancer.

INTRODUCTION: The sensitivity and specificity of immunohistochemistry (IHC) was compared with the standard polymerase chain reaction (PCR)-based method for detecting common activating epidermal growth factor receptor (EGFR) mutations in non-small-cell lung cancer (NSCLC). Additionally, we evaluated predictive value of IHC EGFR mutation-positive status for EGFR tyrosine kinase inhibitor (TKI) treatment outcome and estimated cost-effectiveness for the upfront IHC testing. METHODS: The trial included 79 consecutive EGFR mutation-positive and 29 EGFR mutation-negative NSCLC cases diagnosed with reflex PCR-based testing. Two mutation-specific antibodies against the most common exon 19 deletion, namely E746-A750del (clone SP111) and L858R mutation (clone SP125) were tested by using automated immunostainer. Sixty of 79 EGFR mutation-positive cases were treated with EGFR TKIs for advanced disease and included in treatment outcome analysis. A decision tree was used for the cost-effectiveness analysis. RESULTS: The overall sensitivity and specificity of the IHC-based method compared with the PCR-based method were 84.8% (95% confidence interval [CI] 74.6-91.6) and 100% (95% CI 85.4-100), respectively. The median progression-free survival (PFS) and overall survival (OS) of patients with IHC-positive EGFR mutation status were highly comparable to the total cohort (PFS: 14.3 vs. 14.0 months; OS: 34.4 vs. 34.4 months). The PCR and IHC cost ratio needs to be approximately 8-to-1 and 4-to-1 in White and Asian populations, respectively, to economically justify upfront use of IHC. CONCLUSION: The trial confirmed an excellent specificity with fairly good sensitivity of IHC with mutation-specific antibodies for common EGFR mutations and the accuracy of IHC testing for predicting response to EGFR TKIs. The use of upfront IHC depends mainly on the population EGFR mutation positivity probability.

Brain metastases in lung adenocarcinoma: impact of EGFR mutation status on incidence and survival.

BACKGROUND: The brain represents a frequent progression site in lung adenocarcinoma. This study was designed to analyse the association between the epidermal growth factor receptor (EGFR) mutation status and the frequency of brain metastases (BM) and survival in routine clinical practice. PATIENTS AND METHODS: We retrospectively analysed the medical records of 629 patients with adenocarcinoma in Slovenia who were tested for EGFR mutations in order to analyse the cumulative incidence of BM, the time from the diagnosis to the development of BM (TDBM), the time from BM to death (TTD) and the median survival. RESULTS: Out of 629 patients, 168 (27%) had BM, 90 patients already at the time of diagnosis. Additional 78 patients developed BM after a median interval of 14.3 months; 25.8 months in EGFR positive and 11.8 months in EGFR negative patients, respectively (p = 0.002). EGFR mutations were present in 47 (28%) patients with BM. The curves for cumulative incidence of BM in EGFR positive and negative patients demonstrate a trend for a higher incidence of BM in EGFR mutant patients at diagnosis (19% vs. 13%, p = 0.078), but no difference later during the course of the disease. The patients with BM at diagnosis had a statistically longer TTD (7.3 months) than patients who developed BM later (3.1 months). The TTD in EGFR positive patients with BM at diagnosis was longer than in EGFR negative patients (12.6 vs. 6.8, p = 0.005), while there was no impact of EGFR status on the TTD of patients who developed BM later. CONCLUSIONS: Except for a non-significant increase of frequency of BM at diagnosis in EGFR positive patients, EGFR status had no influence upon the cumulative incidence of BM. EGFR positive patients had a longer time to CNS progression. While EGFR positive patients with BM at diagnosis had a longer survival, EGFR status had no influence on TTD in patients who developed BM later during the course of disease.