Study to Evaluate the Efficacy and Safety of Lutathera in Patients With Grade 2 and Grade 3 Advanced GEP-NET

Inclusion Criteria: * Presence of metastasized or locally advanced, inoperable (curative intent) histologically proven, well differentiated Grade 2 or Grade 3 gastroenteropancreatic neuroendocrine (GEP-NET) tumor diagnosed within 6 months prior to screening. * Ki67 index ≥10 and ≤ 55% * Patients ≥ 15 years of age and a body weight of \> 40 kg at screening * Expression of somatostatin receptors on all target lesions documented by CT/MRI scans, assessed by any of the following somatostatin receptor imaging (SRI) modalities within 3 months prior to randomization: \[68Ga\]-DOTA-TOC (e.g. Somakit-TOC®) PET/CT (or MRI when applicable based on target lesions) imaging, \[68Ga\]-DOTA-TATE PET/CT (or MRI when applicable based on target lesions) imaging (e.g. NETSPOT®), Somatostatin Receptor scintigraphy (SRS) with \[111In\]-pentetreotide (Octreoscan® SPECT/CT), SRS with \[99mTc\]-Tektrotyd, \[64Cu\]-DOTA-TATE PET/CT (or MRI when applicable based on target lesions) imaging. * The tumor uptake observed in the target lesions must be \> normal liver uptake. * Karnofsky Performance Score (KPS) ≥ 60 * Presence of at least 1 measurable site of disease * Patients who have provided a signed informed consent form to participate in the study, obtained prior to the start of any protocol related activities Exclusion Criteria: * Creatinine clearance \< 40 mL/min calculated by the Cockroft Gault method * Hb concentration \< 5.0 mmol/L (\<8.0 g/dL); WBC \< 2x10E9/L (2000/mm3); platelets \< 75x10E9/…