This study has been designed in order to detect EGFR mutation abundance of tissue and concentration of plasma from Advanced Non-small Cell Lung Cancer during treatment with Tyrosine Kinase Inhibitor (TKI) .Through this experiment the investigators aim to evaluate the feasibility of plasma EGFR detection and evaluate the correlation of EGFR mutations and prognosis.

Inclusion Criteria:

• Age older than 18 years and under 75 years
• Histologically and cytologically proven non-small Cell Lung Cancer
• Clinical stages Ⅲ ~ Ⅳ
• Not receive any anti-tumor treatment
• Eastern cooperative oncology group performance status (ECOG PS) =1~2
• Estimated survival time more than 3 months
• EGFR-TKI treatment for first-line or second-line
• Voluntary to participate in this clinical trial and sign the consent form

Exclusion Criteria:

• Patients have received EGFR-TKI therapy before the study
• With other malignancy history in the recent 5 years before the study
• Pregnancy or breast feeding phase
• Inadequate samples for testing
• Follow-up compliance is poor

Patients with stage Ⅲ-Ⅳ NSCLC with EGFR mutations and who began a treatment by TKI .