Outcome for patients diagnosed with advanced lung cancer remains poor; alternative treatment options are urgently needed. Studies in other metastatic cancers indicate radiotherapy to the primary tumour can improve outcomes. The investigators postulate this will also be observed in lung cancer patients. The aim of this pilot study is to assess the safety and feasibility of stereotactic ablative radiotherapy (SABR) to the lung primary prior to standard of care (SoC) systemic therapy in advanced non-small cell lung cancer (NSCLC). Forty patients with advanced (Stage IV) NSCLC will be recruited across the five Peter Mac campuses. Patients will be randomised to receive SoC systemic therapy with or without radiotherapy to the lung primary. Radiotherapy will be delivered before cycle 3 of SoC systemic therapy. Biospecimens will be collected for future translational research. The primary outcome of the study (feasibility of the protocol) will be assessed by the ability to deliver radiotherapy to the lung cancer primary, whilst meeting dose constraints. The study will also 1) evaluate proportion of patients who are willing to be randomised; 2) describe toxicity during the follow up period in each arm; 3) describe progression free survival.