Phase I Trial to Determine the Dose and Evaluate the PK and Safety of Lutetium Lu 177 Edotreotide Therapy in Pediatric Participants With SSTR-positive Tumors

Key Inclusion Criteria: * Participants aged ≥ 2 years and \< 18 years * Confirmed diagnosis somatostatin receptor-positive (SSTR-positive) disease. * Tumor which is relapsed or is refractory to at least one line of previous therapy * Positive SSTR protein expression confirmed by immunohistochemistry of a tumor histology sample * Radioactivity uptake within the primary tumor or metastatic tumor sites measured by locally available SRIs ( 111In-based, 99mTc-based, or 68Ga-based SSTR single-photon emission computed tomography (SPECT)/ computed tomography (CT) or positron emission tomography (PET)/CT imaging, which is higher than the liver uptake) * Participants must have recovered from the acute treatment related toxicities (defined as ≤ grade 1 if not defined in eligibility criteria, excluding alopecia, stable treated electrolyte abnormalities on replacement and stable treated hypothyroidism) of all prior treatment modality prior to entering this trial * In case of sequential treatment followed by SoC or prior therapy, washout period applies before starting targeted RPT Screening Consent Participant/legal guardian is willing to sign a screening consent. The screening consent is to be obtained according to institutional guidelines. Assent, when appropriate, will be obtained according to institutional guidelines. Key Exclusion Criteria: * Known hypersensitivity to Lutetium Lu 177 Edotreotide, DOTA/Edotreotide, or excipients * Previous history of acute leukemia unless in remission for at least two years * Extensive bone/bone marrow involvement as per Investigator's judgement unless peripheral blood stem cells (PBSC) are available at a minimum of 2.5x106 CD34+ cells/kg * Patients who have received previous systemic targeted RPT * Previous treatment with metaiodobenzyl guanidine (MIBG) if the predicted overall exposure is expected to exceed 2 Gy (gray) to the bone marrow or 23 Gy to the kidney. * Previous treatment with external beam radiation therapy (EBRT) if the predicted overall exposure is expected to exceed more than 2 Gy to the bone marrow or 23 Gy to the kidney. * Previous treatment with oncologic immune vaccine or CAR-T cell therapy * Bulky disease in the CNS * Presence of severe renal, hepatic, electrolyte, cardiovascular, or hematological dysfunction * Participants who have received a live-attenuated vaccine up to four weeks prior to enrolment * Pregnant or breastfeeding women. * Other known malignancies. * Serious non-malignant disease.