The purpose of this study is to assess the performance of imaging agent 64Cu-SARTATE in participants with known or suspected Gastroenteropancreatic (GEP) Neuroendocrine Tumors (NETs) as a potential new way to help diagnose NETs.

Up to 63 participants will be recruited in this study and who are confirmed or suspected to have NETs based on biochemical evidence or that of conventional anatomical or molecular imaging.

Inclusion Criteria:

1. Signed informed consent;
2. Age at enrolment ≥ 18 years;
3. Life expectancy ≥ 12 weeks;
4. Known diagnosis of GEP NET or suspicion of GEP NET based on axial imaging (e.g. on CT and/or MRI and/or FDG) and/or biochemical evidence of NET;
5. Adequate recovery from acute toxic effects of any prior therapy;
6. Adequate renal function (eGFR >30 ml/min);
7. Pre-study 68Ga-DOTATATE PET/CT scan performed within 5 weeks, but not closer than 6 hours prior to the administration of 64Cu-SARTATE;

Exclusion Criteria:

1. Female participant who are pregnant or lactating;
2. Male or female participant of childbearing potential not willing to practice an effective method of birth control while participating on the study to avoid possible damage to the foetus. Abstinence is considered acceptable;
3. Participant has received any treatment (including experimental treatment) for their NET in the interval between 68Ga-DOTATATE PET/CT and 64Cu SARTATE PET/CT scan;
4. Any serious medical condition or extenuating circumstance which the investigator believes may interfere with the procedures or evaluations of the study;
5. History of other active malignancy within the last 2 years the exception of adequately treated basal cell carcinoma, squamous cell carcinoma or other non-melanomatous skin cancer, in-situ carcinoma of the uterine cervix, or prostate cancer that is controlled by hormone therapy (patients may continue hormone therapy while on study).
6. Active oncologic therapy within 8 weeks prior to the 68GaDOTATATE PET/CT scan (long-acting somatostatin analogues are permitted and not considered active oncological treatment);
7. Participants with diffuse or infiltrative hepatic involvement based on the pre-study 68Ga-DOTATATE PET/CT scan;
8. Participants with extensive marrow/skeletal involvement (>20 lesions) based on the pre-study 68Ga-DOTATATE PET/CT scan.