How would you approach patients with EGFR mutation positive (exon 19) NSCLC who rapidly progress on front line EGFR inhibition with first generation TKI at first imaging?

This is a difficult challenging situation. I usually repeat tissue biopsy or at least order a liquid bx, confirm that in fact they did have the EGFR mutation and assess for the T790M. I do consider switching to osimertinib if they have the T790M and this was not the EGFR TKI they were on. However ch...