P3.02b-055 Impact of Pemetrexed Chemotherapy in Exon 19 or Exon 21 Mutated NSCLC: Topic: EGFR Clinical

Abstract

EGFR mutation subtype is being increasingly recognized as factor impacting outcome of patients receiving oral TKI in non-small cell lung cancer. Data for the effect of this factor on the outcome in patients receiving chemotherapy is limited. We have the post hoc analysis of the study at our center to answer this question. We completed a study comparing pemetrexed with platinum vs. oral TKI in EGFR mutation positive patients in lung cancer. We analyzed the impact of EGFR mutation subtype, exon 19 and 21 on the PFS and OS of patients treated with pemetrexed (500mg/m2 on day 1) and carboplatin (AUC 5 on day 1) as first line therapy every 21 days. 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 (post 6 cycles, patients were offered maintenance pemetrexed every 21 days). 143 patients received pemetrexed based therapy as first line treatment for stage III/IV NSCLC in the chemotherapy arm. 51 patients (36%) had exon 21 mutation while 92 patients (64%) had exon 19 mutation. Response rates in evaluable patients was 47.7% in exon 19 patients (41 patients, n=86) and 42.9 % in exon 21 patients (18 patients, n=42). There was a differential impact of EGFR mutation on PFS (p=0.028, HR=1.787, 95% CI 1.066- 2.998) in favor of exon 19 mutation. They also had a significant increase in median overall survival (24.5 months, 95% CI 21.3-27.7 months ) over the exon 21 mutated patients (18.1 months,95% Cl 13.5-22.6 months, p=0.002). In this study, EGFR exon 19 mutation had a differential impact on both PFS and OS in Indian patients of advanced-stage NSCLC treated with chemotherapy.