A multicenter phase II study to evaluate the efficacy and safety of gefitinib as first-line treatment for Korean patients with advanced pulmonary adenocarcinoma harboring EGFR mutations

This study was designed to prospectively evaluate the efficacy and safety of first-line gefitinib treatment in patients with advanced pulmonary adenocarcinoma harboring epidermal growth factor receptor (EGFR) mutations and to explore the molecular factors affecting the efficacy of gefitinib. Tumor tissue, derived from either the original tumor or the metastatic or recurrent site was taken from chemo-naïve pts with advanced (stage IIIB, IV, and recurrent) pulmonary adenocarcinoma. Tumor genomic DNA underwent direct sequencing for EGFR exons 18, 19, 20, and 21. Patients with EGFR mutations received 250 mg of gefitinib daily until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). Secondary endpoints were progression free survival (PFS), overall survival (OS) and tolerability. Out of 147 screened patients, 45 pts (31%) had EGFR mutations and received gefitinib. The most common EGFR mutations were in-frame exon 19 deletions (29 pts, 64%) and L858R point mutation in exon 21 (15 pts, 33%). One patient had atypical mutation of L861Q in exon 21. The ORR was 53.3% (95% CI, 38.6-67.9) and disease control rate (DCR) including stable disease was 86.7%. The median progression free survival (PFS) was 398 days and the median overall survival (OS) was 819 days. Treatment was well tolerated. Grade 3/4 adverse events (AEs) were reported by 6 patients and treatment-related Grade 3 AEs by 3 patients. There were no treatment-related Grade 4 AEs. Exploratory subgroup analysis according to the EGFR mutation subtypes was carried out. The ORR and DCR were higher in patients with exon 19 deletions than those with L858R (62.1% vs 33.3%; P = 0.0705 and 96.6% vs 66.7%; P = 0.0062, respectively). All 4 patients with progressive disease had a L858R mutation. No secondary resistant mutations such as T790M mutation or insertions in exon 20 were found in those patients. In addition, OS was significantly better in patients with exon 19 deletions than those with L858R (24-month OS rate was 72.1% vs 32.0%, P = 0.0148). Gefitinib as the first-line treatment for Korean patients with advanced pulmonary adenocarcinoma harboring EGFR mutations was effective and well tolerated. Subgroup analysis suggests that the benefit from gefitinib treatment was more prominent in patients with the exon 19 deletion mutations (ClinicalTrials.gov number, NCT00344773).