A prospective, observational study that assesses the clinical feasibility of ctDNA-based liquid biopsy in patients with oligometastatic NSCLC receiving surgery.

60 eligible patients will be enrolled. Dynamic blood samples before and after surgery and tissue samples will be obtained for exploratory analysis.

Inclusion Criteria:

• Written informed consent must be obtained from patients and ability for patients to comply with the requirements of the study；
• Patients must be a man or woman of more than 18 years;
• ECOG PS ≦1；
• The function of the organs was evaluated by the surgeon to tolerate local surgical treatment；
• The classification was evaluated as simultaneous oligometastases at initial treatment or oligoresidual/oligoprogression/oligorecurrence after induction therapy; [Define: Initial treatment of simultaneous oligometastases: without systemic treatment, at the time of diagnosis, up to 5 metastases and up to 3 organs were involved, excluding pleural metastases or myeloid metastases.

Oligoresidual after induction therapy: after systemic therapy, distant metastases were stable or reduced, primary lesions were stable or reduced, PET/CT metabolism was reduced, and no more than 5 residual lesions and no more than 3 organs were involved.

Oligoprogression after induction therapy: After systemic therapy, some lesions were stable or reduced, while some original lesions were larger than before.

Oligorelapses after induction therapy: after systemic therapy, systemic lesions were stable or reduced, and new local lesions appeared.]

• Lesion evaluation can be surgically removed. [Definition of operable resection: the lesion is limited and can be completely removed through surgery as assessed by the surgeon, with no significant impact on postoperative quality of life. Pulmonary surgical procedures include lobectomy, segmental resection and wedge resection. Pneumonectomy is not included.]

Exclusion Criteria:

• Patients with a confirmed or suspected autoimmune disease;
• Patients with a history of human immunodeficiency virus (HIV) positive or acquired immunodeficiency syndrome (AIDS);
• Patients with a history of any arterial thrombosis within 6 months and history of deep vein thrombosis, pulmonary embolism, or any other severe thromboembolism within 3 months;
• Patients with any unstable systemic disease (eg, active infection, high-risk hypertension, unstable angina, congestive heart failure, etc.);
• Patients with a history of other malignancies in the past 5 years;
• Patients identified by the investigators patients with contraindications to local treatment;
• Patients with serious mental illness;
• Patients who cannot sign informed consent;
• Patients who cannot be followed up as scheduled;

Stage IV NSCLC patients with oligometastases at initial diagnosis or oligoresidual or oligoprogression or oligorelapses after systemic therapy