The purpose of this study is to compare the frequency and abundance of T790M mutation among the different Clinical modes of EGFR-TKI failure.

An observational, non-interventional, multi-central study of comparison of the frequency and abundance of T790M mutation using both amplification refractory mutation system (ARMS) and digital droplet PCR (ddPCR) methods among the different Clinical modes of non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) failure

Inclusion Criteria:

• Histologically confirmed stage IIIB/IV NSCLC.
• Investigator confirmed progression according RECIST 1.1 during EGFR-TKI treatment within 28 days of the enrollment
• Activating mutation (G719A/C/S; Exon 19 insertion/deletion; L858R; L861Q) in the EGFR gene or have had at least partial response with EGFR TKI lasting ≥ 6 months
• Patient must be able to comply with the protocol

Exclusion Criteria:

• Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 defined disease progression for more than 28 days while on previous EGFR-TKI treatment.
• Patient has been treated with any investigational agent for any indication within 4 weeks of study treatment.
• Histologically confirmed small cell lung cancer or other metastatic tumors
• Patient with no histologic or cytological diagnosis.

Patients with Non small cell lung cancer (NSCLC) after EGFR-TKI failure