177Lu-DOTATATE Modified Delivery Based on Individualized Dosimetry

Eligibility 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™.