Multi-modal Characterisation of Gastroenteropancreatic Neuroendocrine Tumours (GEP-NETs) Treated With Targeted Radionuclide Therapy (TRT): Prospective Interventional Multicentre National Cohort

Inclusion Criteria: * According the MDT decision to refer to PRRT 1. Histologically confirmed diagnosis of unresectable GEP-NETs whatever the grade or NETs of unknown primary but suspected of GEP origin 2. Metastastic and progressive according RECIST 1.1 criteria 3. At least 1 measurable site of disease per RECIST v1.1 using contrast-enhanced CT or magnetic resonance imaging 4. SSTR+ disease, as evidenced by PET-DOTATOC performed within 4 months prior to inclusion (lesion uptake greater than liver physiological uptake) 5. The majority of the lesions and all RECIST 1.1 selected target lesion have to be SSTR+. * Karnofsky performance status scale ≥ 60 * Live expectancy \>6 months * Patients ≥ 18 years of age Exclusion Criteria: * Known pregnancy or breastfeeding women * Known hypersensitivity to 177Lu, octreotate, DOTA, 68Ga, Edotreotide, * Known hypersensitivity to lysine, arginine, or any excipient of the nephroprotective amino acid solution (AAS) given concomitantly to the 177Lu-DOTATATE infusion. * Contraindication to MRI and technical impossibility of MRI * Prior external beam radiation therapy (EBRT) of GEP-NET lesions or liver selective internal radiation therapy within 12 weeks before inclusion, if extensive * Other systemic antitumor treatment (non-radioactive, excluding somatostatin analogues) not interrupted for at least 4 weeks * Mixed Neuroendocrine-Non-endocrine Neoplasms (MiNEN) * Neuroendocrine carcinoma * Uncontrolled brain metastasis for at least 3 months * NYHA 3 or 4 heart failure * Inability to discontinue delayed-acting somatostatin analogues at least 28 days prior the PRRT or rapid-acting somatostatin analogues at least 24 hours prior the PRRT * Non-adequate bone marrow, liver and renal function within 1 month prior the PRRT as assessed by the following laboratory tests: * Platelet count \< 75,000/mm3 * Haemoglobin ≤ 8,0 g/dL * Total bilirubin \> 3 ULN * Neutrophils \< 1000/mm3 * Prothrombin time \< 70% unless albumin \> 30g/L * Albumin \<30g/L unless prothrombin time \> 70 % * Glomerular Filtration Rate (GFR) \< 35 mL/min/1.73 m2 * Prior peptide receptor radionuclide therapy (PRRT) * Other progressive cancer excluding in situ cervical cancer and basal or squamous cell skin cancer within the last 3 years * Patient refusal to give written informed consent * Subject deprived of freedom, subject under a legal protective measure * No affiliation to a social security regimen or CMU * Patient under State Medical Aid