Alectinib Followed by Concomitant Consolidation Radiation Therapy in Advanced NSCLC With ALK-rearrangement (A-SAB)

Inclusion Criteria: 1. Histological or cytological confirmed NSCLC: * Stage IV NSCLC OR * Stage III NSCLC not suitable for surgery or radiochemotherapy OR * Recurrent NSCLC after previous surgery (not amendable for curative multimodal therapy) 2. ALK-rearrangement 3. Adequate organ function to tolerate alectinib and clinical tolerance to alectinib 4. Stable disease (SD) or partial response (PR) after 2-3 months induction treatment with alectinib 5. Maximum 5 tumour lesions +/- thoracic lymph nodes active on an 18F-FDG-PET scan post induction treatment with alectinib 6. All active tumour lesions amendable to RT under the following conditions: * All metastases possible to treat with * Extracranial metastases: SBRT of at least 7 Gy x 5 (corresponding to 50 Gy EQD2 using alfa/beta 10Gy) * Intracranial metastases: SRS or f-SRS * The primary tumour and/or lymph nodes and/or pulmonary metastases amendable to SBRT (≥ 7Gy x 5, see above) or moderately hypofractionated RT of 3 Gy x 15 (corresponding to 49 Gy EQD2 using alfa/beta 10Gy) 7. Adequate organ function to tolerate SBRT/RT: * Fulfilment of dose constraints to adequate organs at risk 8. ECOG performance status (PS) 0-2 9. FEV1 ≥1 litre (only applicable for lung targets) 10. Age ≥ 20 years 11. Measurable lesions according to RECIST v 1.1 12. Signed written informed consent Exclusion Criteria: 1. Leptomeningeal carcinosis (on MRI or in cerebrospinal fluid (CSF)) 2. Persistent malignant pleural effusion, malignant pericardial effusion or malignant ascites after induction treatment 3. PD after 2-3-month-induction treatment with alectinib 4. Previous TKI, chemotherapy or immunotherapy (previous adjuvant chemotherapy for early stage NSCLC is allowed) for metastatic NSCLC 5. Previous RT for NSCLC (any stage) 6. Previous RT for any other cancer within the last 3 years possibly interfering with the planned RT within this study 7. Life expectancy of less than 6 months 8. Inability to understand given information or undergo study procedures according to protocol. 9. Has evidence or a past medical history of interstitial lung disease or active, non-infectious pneumonitis or known pulmonary fibrosis. 10. Pregnant or breast-feeding. Patients must agree to use safe contraception during and for 3 months after study treatment.