Pulse Radiotherapy to Overcome Metastatic Immune System Evasion in Lung Cancer

Inclusion Criteria: * Participants must be ≥ 18 years old * Ability to provide written informed consent * Actively receiving PD(L)-1 inhibitors * Progressive disease defined as per RECIST criteria 1.1 on CT metrics as a greater than 20% increase in the sum measurement of lesions, non-target unequivocal progressive disease or a new lesion on CT. * Radiological progression to ≥ 5 disease sites. Progression at the primary tumor site should be counted within the total number of progressive lesions. For patients with lymph node metastases, each node is counted as one site of metastasis. * Participants must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. * Patients with brain metastasis are allowed and should be treated as per standard of care * All sites of disease can, in the opinion of the investigator, be safely treated and targetable with high-to-intermediate or low dose radiotherapy (taking into account prior local therapy, organ function and underlying medical condition such as inflammatory bowel disease, pulmonary fibrosis, etc.) * Patients with prior metastases that have been treated with ablative therapies (e.g. radiotherapy, surgery or radiofrequency ablation) before their current line of systemic therapy, are eligible. * Patients receiving additional systemic therapy agents such as chemotherapy are eligible, provided the other systemic agents are temporarily halted during radiation treatment. Exclusion Criteria: * Pregnant or breastfeeding individuals are excluded. * Medical conditions that would hinder the safe administration of radiotherapy or follow-up. * Patients who are ineligible for immunotherapy. * Patients with a history of pneumonitis are excluded. * Presence of an active autoimmune disease.