Inclusion Criteria:

          -  Age ≥18 years

          -  Metastatic NSCLC enrolled in our CRCHUM Lung Cancer Registry and co-enrolled to the
             PERa registry

          -  Ability to provide written informed consent

          -  Eastern Cooperative Oncology Group (ECOG) performance status 0-3

          -  Oligoprogression to 1-5 extracranial lesions ≤ 5cm and involving ≤ 3 organs.
             Progression at the primary tumor site should be counted within the total of 5 lesions.
             For patients with lymph node metastases, each node is counted as one site of
             metastasis.

          -  Oligoprogression while on ICI or TKI (any line)

          -  Patients with brain metastasis are allowed; brain metastasis are not counted in the
             maximum number of lesions 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 SABR (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.

        Exclusion Criteria:

          -  Any lesion beyond 5 cm

          -  Pregnancy or breastfeeding

          -  Any medical condition that could, in the opinion of the investigator, preclude
             radiotherapy or prevent follow-up after radiotherapy.

          -  Presence of spinal cord compression Metastatic disease that invades the GI tract
             (including esophagus, stomach, small or large bowel)