Stereotactic Ablative Radiotherapy in Synchronous and Metachronous Oligo-Metastatic Non Small Cell Lung Cancer

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0-2 * histologically confirmed NSCLC * synchronous oligo-M NSCLC as determined by Positron emission tomography- computed tomography (PET/CT) and brain MRI (AJCC 8th edition) * metachronous oligo-M NSCLC (oligo-persistence, oligo-progressive, oligo-induced) as determined by PET/CT and brain magnetic resonance imaging (MRI) (AJCC 8th edition) * patients with at least one target to be treated by SABR at the body * patients with brain metastases synchronous to the body will be enrolled only if amenable to radiosurgery (the number of brain metastases does not enter into the count of the number of oligo-M) * patients with a previous history of brain metastases will be enrolled only if the previously treated brain metastases are in control Exclusion Criteria: * Ability to understand and the willingness to sign an institutional review board (IRB)- approved informed consent document (either directly or via a legally authorized representative) * Inability to safely treat target lesions * Pregnant women are excluded from this study because radiation therapy has known potential for teratogenic or abortifacient effects.