Stereotactic Body Radiotherapy for Oligo-Progression Metastatic Non-Small Cell Lung Cancer

Inclusion Criteria: * Age ≥ 18 years. Gender is not limited. * Histologically and/or cytologically confirmed stage IV metastatic NSCLC. * Eastern Cooperative Oncology Group (ECOG) score of 0-2. * Patients who had prior first-line chemotherapy with clinical benefit lasting for ≥3 months. * Driver gene-negative NSCLC patients with oligo-progression during first-line chemotherapy combined with Immune Checkpoint Inhibitors (ICI). Driver gene-positive NSCLC patients, such as epidermal growth factor receptor (EGFR) mutation or anaplastic lymphoma kinase (ALK) fusion positivity, are allowed to enroll if oligo-progression occurred during treatment with first-line chemotherapy combined with bevacizumab ± ICI after failure of Tyrosine Kinase Inhibitor (TKI) therapy. * Progressive sites were assessed as ≤5 according to RECIST v1.1 criteria combined with positron emission tomography / computertomography (PET/CT), and all were located extracranially. Progressive lymph node lesions are counted by region, with each lymph node region amenable to concurrent SBRT (which may contain multiple progressive lymph nodes) counted as 1 progressive site. * All progressive sites should be visible on radiologic imaging and assessed as suitable for SBRT treatment by a radiotherapist. * Intracranial progressive lesions and symptomatic lesions can be treated with palliative radiotherapy and local therapy prior to enrollment and are not counted within the oligo-progressive sites. * Expected survival time greater than 3 months. * Comprehensive examination completed within 28 days prior to enrollment in the study and a complete blood count/differential, collected within 15 days, showing that the patient has normal internal organ function and normal bone marrow function. * Negative serum or urine pregnancy test in females of childbearing age within 14 days prior to study enrollment. * Patients are willing to provide written informed consent and must be willing to adhere to the prescribed follow-up schedule. Exclusion Criteria: * Currently participating in an interventional clinical study treatment that may affect this study, or have been treated with another investigational drug or investigational device that may affect this study within 4 weeks prior to first treatment. * Pregnant or lactating women. * Progression sites deemed unsuitable for SBRT treatment as assessed by radiotherapy specialists. * Presence of untreated intracranial metastases or symptomatic progressive sites. * History of malignancy other than NSCLC or untreated primary malignancy within the past 3 years. * Serious active comorbidities that would interfere with treatment in this study. * History or evidence of disease that could interfere with the results of the trial, prevent the subject from participating in the study throughout, abnormal values of treatment or laboratory tests, or other conditions that, in the opinion of the investigator, make enrollment inappropriate.