Inclusion Criteria:  histological confirmed diagnosis of NSCLC and EGFR mutation in exon 18-21; locally advanced inoperable or metastatic disease (stage III and IV according to 8th edition of the TNM classification for lung cancer); first line treatment with the third generation EGFR TKI, osimertinib; age >18 years written informed consent  Exclusion Criteria:  Patients who receive study drugs in clinical trials will be excluded.