Patients who was confirmed stage IV (according to International Association for the Study of Lung Cancer（IASLC） TNM staging, 2009) non-small cell lung cancer (NSCLC) by histology or cytology between year 2009 to 2013, harboring EGFR mutant type (19 and/or 21 exon mutation).
Appraisable disease, that is there must be at least one lesion with the longest diameter\>10mm according to Recist 1.1 criterion (by contrast CT).
Patients who take EGFR-TKI as first/second line therapy.
You may not be if
Patients who has taken EGFR-TKI before.
Patients who take EGFR-TKI as third or more line.
Patients who take EGFR-TKI concurrent with chemotherapy or other anti-tumor drug.
The evaluated lesions has treated with radiotherapy before or concurrent with EGFR-TKI.
Patients whose EGFR expression is positive by immunochemical and/or EGFR amplification is positive by Fluorescence In Situ Hybridization(FISH), without mutation detection evidence.
