A phase II study of erlotinib monotherapy in pre-treated non-small cell lung cancer without EGFR gene mutation who have never/light smoking history: re-evaluation of EGFR gene status (NEJ006/TCOG0903)

Abstract

Objectives: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors are particularly effective in non-small cell lung cancer (NSCLC) patients harboring active EGFR mutations. However, some studies have reported survival benefits in NSCLC patients with wild-type EGFR upon erlotinib treatment. This trial was conducted to evaluate the efficacy of erlotinib monotherapy and investigate the predictive values of several biomarkers.

Patients and methods: Patients with previously treated NSCLC but without EGFR gene mutations that had never or light smoked were eligible for this study. Gene status screening was performed using the PNA-LNA PCR clamp method. Erlotinib was administered until disease progression or unacceptable toxicities occurred. EGFR gene status was re-evaluated using the fragment method to detect exon 19 deletions and the Cycleave-PCR method to detect point mutations. Expression of hepatocyte growth factor (HGF), Met, and thymidylate synthase (TS) were evaluated using immunohistochemistry.

Results: Forty-seven patients were enrolled in the study between March 2010 and November 2011. Objective response rate (ORR) and disease control rate (DCR) were 15.2% and 41.3%. Re-evaluations for EGFR gene were performed in 32 tumor samples. EGFR gene mutations were found in eight samples (5:exon 19 deletion, 2:G719X, 1:L858R). Six patients had PR and two had SD among these eight patients. A total of 24 patients were confirmed as wild-type EGFR using different methods. ORR and DCR were 4.2% and 41.7%. The median progression free survival (PFS) and median survival times were 2.0 and 6.0 months, respectively. Patients with tumors expressing HGF showed shorter PFS but not MET or TS.

Conclusions: Re-examination of EGFR gene status using different detecting method or different sample should be considered to grasp a chance of erlotinib treatment after first line treatment. In confirmed EGFR wild NSCLC, negative HGF staining could be a biomarker for longer PFS by erlotonib treatment.

Keywords: EGFR-TKI; Erlotinib; HGF; Re-evaluation; Wild type EGFR.