Key Inclusion Criteria:

          1. GEP-NET cohort: presence of metastasized or locally advanced, inoperable (curative
             intent), histologically proven, G1 or G2 (Ki-67 index =< 20%), well differentiated
             GEP-NET.

             or PPGL cohort: presence of metastasized or locally advanced, inoperable (curative
             intent), histologically proven PPGL.

          2. Patients from 12 to < 18 years of age at the time of enrollment.

          3. Expression of somatostatin receptors confirmed by a somatostatin receptor imaging
             (SRI) modality within 3 months prior to enrollment, with tumor uptake observed in the
             target lesions more or equal to the normal liver uptake.

          4. Performance status as determined by Karnofsky score >= 50 or Lansky Play-Performance
             Scale score >= 50.

          5. Parent's ability to understand and the willingness to sign a written informed consent
             document for adolescents as determined by local regulations. Adolescents will sign
             assent along with parental/legal guardian consent or will co-sign consent with
             parent/legal guardian in accordance with local regulation, prior to participation in
             the study.

        Key Exclusion Criteria:

          1. Laboratory parameters:

               1. Estimated creatinine clearance calculated by the Cockroft-Gault method < 70
                  mL/min

               2. Hb concentration <5.0 mmol/L (<8.0 g/dL); WBC <2x109/L; platelets <75x109/L.

               3. Total bilirubin >3 x ULN for age.

               4. Serum albumin <3.0 g/dL unless prothrombin time is within the normal range.

          2. Established or suspected pregnancy.

          3. Breastfeeding female patients unless they accept to discontinue breastfeeding from the
             1st dose until 3 months after the last administration of study drug.

          4. Female patients of child-bearing potential, unless they are using highly effective
             methods of contraception during treatment and for 6 months after the last dose of
             Lutathera.

          5. Sexually active male patients, unless they agree to remain abstinent or be willing to
             use effective methods of contraception.

          6. Patients for whom in the opinion of the investigator other therapeutic options are
             considered more appropriate than the therapy offered in the study, based on patient
             and disease characteristics.

          7. Current spontaneous urinary incontinence.

          8. Other known co-existing malignancies except non-melanoma skin cancer and carcinoma in
             situ of the uterine cervix, unless definitively treated and proven no evidence of
             recurrence for 5 years.

          9. Hypersensitivity to the study drug active substance or to any of the excipients.

         10. Patients with any other significant medical, psychiatric, or surgical condition,
             currently uncontrolled by treatment, which may interfere with the completion of the
             study.

         11. Patient with known incompatibility to CT Scans with I.V. contrast due to allergic
             reaction or renal insufficiency. If such a patient can be imaged with MRI, then the
             patient would not be excluded.

         12. Patients who received any investigational agent within the last 30 days.