A Prospective, Randomized, Controlled, Open-label, Multicenter Trial to Evaluate Efficacy, Safety and Patient-reported Outcomes of Peptide Receptor Radionuclide Therapy (PRRT) with Lutetium (177Lu) Edotreotide compared to Best Standard of Care in Patients with Well-differentiated Aggressive Grade 2 and Grade 3, Somatostatin Receptor‑positive (SSTR+), Neuroendocrine Tumors of GastroEnteric or Pancreatic Origin (COMPOSE)