In order to be eligible to participate in this study, an individual must meet all of the following criteria. A physical, with vital signs, concomitant medication review, and medical history must be completed within 60 calendar days to confirm appropriateness of Lutathera treatment as well as to foundation for listed criteria.

• Provision of signed and dated informed consent form.
• Stated willingness to comply with all study procedures and availability for the duration of the study.
• Aged ≥ 18 years at time of consent.
• Pathologically confirmed (histology or cytology) malignant neoplasm that is determined to be a well-differentiated neuroendocrine tumor (Ki-67 ≤ 20%) with the primary tumor location known or believed to be gastroenteropancreatic origin (GEP-NET)
• Disease measuring ≥ 1.5 cm in diameter on CT or MRI as measured per RECIST that shows uptake > liver background on sstr2 PET/CT with any FDA approved sstr2 imaging agent. SSTR2 PET/CT must have been obtained within 90 days prior to scheduled C1D1 of Lutathera.
• Recommended to receive LUTATHERA® therapy for unresectable and/or metastatic neuroendocrine disease.
• Adequate performance status (ECOG of 0 or 1; or Karnofsky performance status of ≥70).
• Agrees to contraception during therapy.
• Neutrophil count within normal limits within 28 days of treatment day 1.
• Platelet count within normal limits within 28 days of treatment day 1.
• Ability to take oral medication and be willing to adhere to the treatment regimen
• For individuals of reproductive potential: agreement to use effective birth control
• Agreement to adhere to Lifestyle Considerations throughout study duration: abstain from caffeine or xanthine-containing products as well as alcohol before the start of cycle dosing and through the cycle's final blood sample; minimize social interactions during low blood counts.

• Individuals who are pregnant or lactating (note: potential participants should not engage in 'pump & dump' strategy; lactation must be discontinued).
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection (requiring inpatient admission or a delay to start of therapy), fever, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Surgery, radiation therapy, or chemotherapy ≤ 4 weeks of C1D1 (Toxicities from prior therapies should have resolved to ≤ CTCAE grade 1 or a new baseline established).
• Prior peptide-receptor radiotherapy (PRRT).
• Therapeutic investigational drug within 4 weeks of C1D1 (imaging agents are acceptable).
• A concurrent malignancy that, in the opinion of the investigator, would cause a safety risk by delaying therapy or confound/negatively impact study objectives (documentation of the rationale must be provided)
• Prior external beam radiation dose to the kidneys of >10 Gy (mean dose to functional renal volume).
• Prior external beam radiation (including brachytherapy) involving 25% of the bone marrow (excluding scatter doses of ≤ 5 Gy) as estimated by a radiation oncologist.
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to Octreoscan® or Netspot™.