Switch Maintenance Tyrosine Kinase Inhibitors in EGFR Mutation Positive Metastatic Non-squamous NSCLC: Experience from the real world.

BACKGROUND: Induction pemetrexed platin doublet is the standard of care in locally advanced and metastatic non squamous NSCLC. Maintenance TKI has been successfully explored to sustain benefit achieved after induction therapy especially in EGFR mutation positive NSCLC. The aim of this study is to evaluate outcomes with maintenance TKI in EGFR mutation positive metastatic non squamous NSCLC after induction pemetrexed-platin doublet. The objective is to calculate progression freesurvival rate, overall survival rate and factors affecting outcomes.

MATERIAL AND METHODS: Data of patients with locally advanced and metastatic non squamous NSCLC who received induction pemetrexedplatin doublet and later went on to receive maintenance TKI in view of EGFR mutation positive (N=80) were retrieved from prospectively maintained lung cancer database registered between June 2011 till March 2014. Kaplan Meir survival analysis was used for progression free survival and overall survival. Log rank test was used to evaluate factors affecting outcome.

RESULT: Median follow up is 19 months. Out of 80 EGFR mutation positive patients, 35 patients (44%) achieved partial response while 45 (56%) had stable disease after six cycles of induction pemetrexed platin doublet. Gefitinib was the most common TKI used in 54 patients (67%) compared to erlotinib in 26 patients (33%) as maintenance therapy. Median Progression free survival and overall survival are 11 months and 22 months respectively. Patients receiving maintenance TKI after partial response to induction chemotherapy have superior survival compared to patients who had stable disease after induction chemotherapy. (25 months Vs 20 months; p=0.01) Conclusion: Use of maintenance TKI after induction chemotherapy delays disease progression and improves survival in EGFR mutation positive NSCLC. Patients achieving partial response compared to stable disease with induction chemotherapy have superior outcomes with maintenance TKI.