Efficacy of gefitinib in epidermal growth factor receptor-activating mutation-positive nonsmall cell lung cancer: Does exon 19 deletion differ from exon 21 mutation?

BACKGROUND: This study was designed to evaluate the differential effect of epidermal growth factor receptor (EGFR) mutation status (exon 19 vs. 21) on progression-free survival (PFS) and overall survival (OS) in treatment-naïve advanced EGFR mutation-positive nonsmall cell lung cancer (NSCLC) treated with gefitinib as first-line agent.

METHODS: This was a post hoc analysis of EGFR-mutated (exon 19 and 21) advanced-stage (Stage IIIB or IV), chemotherapy-naive NSCLC patients treated with gefitinib as first line in a phase 3 randomized study. Patients were treated with gefitinib 250 mg daily. Patients underwent axial imaging for response assessment on D42, D84, D126, and subsequently every 2 months till progression. Responding or stable patients were treated until progression or unacceptable toxicity. SPSS was used for statistical analysis. Kaplan-Meier method was used for survival estimation and log-rank test for comparison. Cox proportion hazard model was used for multivariate analysis.

RESULTS: One hundred and forty-one patients were eligible for analysis, of which 78 were males and 63 were females. A total of 127 patients (90.1%) were ECOG 0-1 while 14 patients (9.1%) were ECOG >1. Exon 21 mutation was present in 65 patients (46.1%) and exon 19 mutation in 76 patients (53.9%). One hundred and thirty-three of 141 patients were evaluable for response. Response rate of patients having exon 19 mutation was 72.9% (51 patients, n = 70) while it was 55.6% in patients having exon 21 mutation (35 patients, n = 63) (P = 0.046). Median PFS in exon 19-mutated patients was 9.3 months (95% confidence interval [CI] 6.832-11.768) compared to 7.8 months (95% CI 5.543-10.0) (P = 0.699) in exon 21-mutated patients. The median OS in exon 19-mutated patients was 19.8 months (95% CI 16.8-22.7), and it was 16.5 months (95% CI 10.9-22.1) in exon 21-mutated patients (P = 0.215).

CONCLUSION: There were no differential outcomes in the Indian patients of advanced-stage NSCLC with exon 19 and 21 EGFR mutations treated with gefitinib.