Inclusion Criteria:

• Presence of metastasized or locally advanced neuroendocrine tumor, inoperable (curative intent) at enrollment time, and regardless of the origin of the tumor.
• Ki67 index ≤ 20%
• Patients progressive under SSA (any dose) at the time of enrollment
• Target lesions over-expressing somatostatin receptors according to an appropriate imaging method (e.g. 111In-pentetreotide (Octreoscan) imaging or 68Ga-DOTA0-Tyr3-Octreotate (or 68Ga-edotreotide) imaging)

Exclusion Criteria:

• Either serum creatinine >150 μmol/L (>1.7 mg/dL), or creatinine clearance <50 mL/min calculated by the Cockroft Gault method, eventually confirmed by measured creatinine clearance (or measured glomerular filtration rate (GFR) using plasma clearance methods, not gamma camera-based) <50 mL/min (the measured creatinine clearance / GFR is required only as confirmatory exam).
• Hb concentration <5.0 mmol/L (<8.0 g/dL); WBC <2x109/L (2000/mm3); platelets <75x109/L (75x103/mm3).
• Total bilirubin >3 x ULN.
• Serum albumin <3.0 g/dL unless prothrombin time is within the normal range.
• Pregnancy or lactation.
• For female patients of childbearing potential (defined as < 2 years after last menstruation and not surgically sterile) and male patients, who are not surgically sterile or with female partners of childbearing potential: absence of effective, non-hormonal means of contraception (intrauterine contraceptive device, barrier method of contraception in conjunction with spermicidal gel).
• Any surgery, radioembolization, chemoembolization, chemotherapy and radiofrequency ablation within 12 weeks prior to enrollment.
• Interferons, Everolimus (mTOR-inhibitors) or other systemic therapies within 4 weeks prior to enrollment.
• Known brain metastases, unless these metastases have been treated and stabilized.
• Uncontrolled congestive heart failure (NYHA II, III, IV).
• Uncontrolled diabetes mellitus as defined by a fasting blood glucose >2 ULN.
• Any patient receiving treatment with short-acting Octreotide, which cannot be interrupted for 24 h before and 24 h after the administration of 177Lu-DOTA0-Tyr3-Octreotate, or any patient receiving treatment with Octreotide LAR, which cannot be interrupted for at least 4 weeks before the administration of 177Lu-DOTA0-Tyr3-Octreotate, unless the tumor uptake on target lesions is at least as high as normal liver uptake.
• Patients with any other significant medical, psychiatric, or surgical condition, currently uncontrolled by treatment, which may pose a risk to the patient safety
• Prior external beam radiation therapy to more than 25% of the bone marrow.
• Current spontaneous urinary incontinence making impossible the safe administration of the radioactive IMP.
• Other known co-existing malignancies except non-melanoma skin cancer and carcinoma in situ of the uterine cervix, unless definitively treated and with no evidence of recurrence.
• Patients who have not provided a signed informed consent form to accept this treatment.