First-line Immunotherapy-based Standard of Care and Local Ablative Treatments for Oligometastatic Non-small Cell Lung Cancer Patients.

RLT of all metastatic sites. The possible RLT options will be SBRT, interventional radiology and/or minimally invasive surgery. Depending on the metastatic site, access and patient condition, the best RLT should be initially discussed in a case-to-case basis at the local multidisciplinary board (MTB). The primary tumour and initially invaded lymph nodes should be treated during the maintenance phase. Curative-intent approach modalities (e.g. hypofractionated intensity-modulated thoracic radiation therapy or surgery) should be discussed at the local MTB.

Current French SoC will be used. Main SoC-based immunotherapy includes: * Platinum-based chemotherapy combined with an anti PD-1 immunotherapy (pembrolizumab). Pemetrexed-platinum combinations may be used in non- squamous carcinoma, while paclitaxel-platinum combination is favoured in squamous carcinoma. * Anti PD-1 monotherapy if PD-L1 ≥ 50% is a possible alternative (pembrolizumab or atezolizumab or cemiplimab). Other alternatives include nivolumab-ipilimumab-chemotherapy or durvalumab-tremelimumab-chemotherapy association. Bevacizumab is not allowed given possible interactions with RLT. Maintenance/Immunotherapy alone will be pursued at the investigator's discretion according to the standard procedures (toxicity, progression, choice of the patient...).