Efficacy of Second-Line Pemetrexed-Carboplatin in EGFR-Activating Mutation-Positive NSCLC: Does Exon 19 Deletion Differ from Exon 21 Mutation?

Background It is unknown whether the outcomes of second-line pemetrexed-carboplatin chemotherapy administered after progression on gefitinib are dependent on type of EGFR mutation present at baseline. Method Adult non-small-cell lung cancer patients, with exon 19 deletion or exon 21 L858R mutation, who progressed on gefitinib and received pemetrexed-carboplatin chemotherapy were selected for this analysis. Result 55 patients received pemetrexed-carboplatin as second-line treatment. Response rates in evaluable patients were 39.3% in exon 19 patients (n = 28) and 33.3% in exon 21 patients (n = 15) (p = 0.752, Fisher's exact 2-sided p value). The median PFS in exon 19 and 21 cohorts was 5.900 months (95% CI: 4.274-7.526) and 4.767 months (95% CI: 1.374-8.159), respectively. The median overall survival in exon 19 patients was (11.8 months, 95% CI: 9.916-13.684 months) significantly better than that seen in exon 21 mutation patients (6.2 months, 95% CI: 4.215-8.118 months, p = 0.024) on univariate analysis; however, on multivariate analysis, this association was not confirmed (HR = 0.361, 95% CI: 0.090-1.439, p = 0.149). Conclusion Exon 19 deletion has no impact on PFS and OS in EGFR-mutated patients treated with second-line pemetrexed-carboplatin.