Lutetium 177Lu-Edotreotide Versus Best Standard of Care in Well-differentiated Aggressive Grade-2 and Grade-3 GastroEnteroPancreatic NeuroEndocrine Tumors (GEP-NETs) - COMPOSE

Inclusion Criteria: * Patients aged ≥ 18 years. * Histologically confirmed diagnosis of unresectable, well-differentiated GastroEnteroPancreatic NeuroEndocrine Tumors (GEP-NETs). measurable site of disease per RECIST v1.1 (Response evaluation criteria in solid tumors) using contrast computed tomography (CT) / magnetic resonance imaging (MRI). * Somatostatin receptor-positive (SSTR+) disease. Exclusion Criteria: * Known hypersensitivity to Lutetium 177Lu, edotreotide, DOTA (dodecane tetraacetic acid), any of the comparators, or any excipient or derivative (e.g. rapamycin). * Prior (Peptide Receptor Radionuclide Therapy) PRRT. * Any major surgery within 4 weeks prior to randomization in the trial. * Therapy with an investigational compound and/or medical device within 30 days or 7 half-life periods (whichever is longer) prior to randomization. * Other known malignancies. * Serious non-malignant disease. * Renal, hepatic, cardiovascular, or hematological organ dysfunction, potentially interfering with the safety of the trial treatments. * Pregnant or breastfeeding women. * Patients not able to declare meaningful informed consent on their own or any other vulnerable population to that.