Optimizing Sequential Treatment With EGFR Tyrosine Kinase Inhibitor With a Simulation of the T790M Mutation Rate in -Mutated Lung Cancer.

INTRODUCTION

The mutation rate of T790M might change the effective therapeutic sequence of EGFR tyrosine kinase inhibitors (TKIs). This simulation estimates the T790M positivity rate required for first-line first- or second-generation EGFR TKI to exceed overall progression-free survival (PFS) of first-line osimertinib.

METHODS

The PFS of each treatment with EGFR TKIs as first-line treatment, with osimertinib as second-line treatment among T790M-positive cases, and chemotherapy as second-line treatment among T790M-negative cases was set based on phase 3 trials. Overall PFS A of "upfront osimertinib" and overall PFS B of "first- or second-generation EGFR TKIs followed by osimertinib or chemotherapy" were simulated at different T790M mutation rates, to estimate the T790M mutation rate at which PFS B exceeds PFS A.

RESULTS

Upfront osimertinib: In the setting of PFS of 19 months with first-line osimertinib, the median overall PFS A was 24.8 months (95% confidence interval [CI]: 21.6-28.0 mo). Upfront first- or second-generation EGFR TKI: When the T790M positivity rate was set to 50% and the PFS of second-line osimertinib was 10 months, the total median PFS (PFS B) was 20.2 months (95% CI: 17.5-22.9 mo). Even at a T790M mutation rate of 100%, PFS B (24.7 mo; 95% CI: 21.9-27.9 mo) was shorter than PFS A.

CONCLUSIONS

Even with a T790M mutation rate of 100%, upfront osimertinib treatment is associated with better median PFS than the upfront treatment with first- or second-generation EGFR TKIs. Consistent with the results of the FLAURA trial, with regard to EGFR TKI monotherapy in the first-line treatment, upfront osimertinib would contribute to good prognosis.