Conduct a prospective study in multicenter to confirm the value of circulating tumor DNA in longitudinal monitoring of stage III-IV lung cancer patients.

The study consists of two phases, the first stage is the exploratory stage of blood collection point which is the appropriate effective time after chemotherapy, radiotherapy, targeted therapy. The second phase, which is the expansion of the first phase, is to determine the precise leading time of ctDNA relative to tumor biomarkers or image evaluation in determining the efficacy of advanced NSCLC cancer therapy. Both stages were divided into three subgroups: the chemotherapy group, the radiotherapy group, and the targeted therapy group.

Inclusion Criteria:

1. Greater than 18 years old;
2. Patients with stage III-IV NSCLC;
3. Have the tissue specimens (fresh or wax blocks) before this treatment;
4. PS<=2 in radiotherapy/ chemotherapy group; PS<=3 in targeted therapy group
5. Signing informed consent;

Exclusion Criteria:

1. Multiple primary lung cancer;
2. Incorporating any unstable systemic disease;
3. Histology is not NSCLC;
4. Unqualified blood samples;
5. Patients lacking any one of the detection points.

The population will be drawn from Oncology Department of multicenters. The enrolled patients must be patients with stage III-IV NSCLC according to the 8th edition of the TNM Classification of the International Association for the Study of Lung Cancer (IASLC), must be greater than 18 years old and must have the tissue specimens (fresh or wax blocks) before this treatment. The exclusion criteria are as followed: (1) Multiple primary lung cancer;(2) Incorporating any unstable systemic disease; (3) Histology is not NSCLC; (4)Unqualified blood samples; (5) Patients lacking any one of the detection points. All of the patients signing informed consent were not involved in the recruitment and conduct of the study