Randomized Interval Assessment Trial of Lu177-Dotatate in Slowly Progressive G1-2 Advanced Midgut Neuroendocrine Tumors

This is a randomized Phase II/late phase I de-escalation clinical trial with approved investigational medicinal products in new use condition, low intervention. Disease under study Patients with unresectable or metastatic, slowly progressive, well-differentiated (Grade1 and Grade2), somatostatin receptor-positive midgut neuroendocrine tumors (GEP-NETs). It is planned to randomize 166 patients with a histologically confirmed diagnosis of slowly progressive grade 1 or grade 2 advanced midgut neuroendocrine tumors (NETs) candidates to receive 177Lu-Dotatate targeted radioligand therapy (RLT). Patients are required to have SSTR+ disease, as evidenced on somatostatin receptor imaging. Patients will be randomized into two arms: 1. control arm: regimen 177Lu-Dotatate every 8 weeks (q8w) 2. experimental arm: regimen 177Lu-Dotatate every 16 weeks (q16w) Research hypothesis: Less intensive somatostatin-receptor (SST) targeted radioligand therapy (RLT) (7.4 GBq/cycle 177Lu-Dotatate every 16 weeks x 4 cycles) is associated with less severe hematological toxicities and may mitigate the risk to develop therapy-related myeloid neoplasms (t-MN) with similar antitumor efficacy in slowly growing gastrointestinal grade 1-2 NETs.

Inclusion Criteria: 1. Patients who have histologically confirmed diagnosis of unresectable, advanced or metastatic midgut NETs (originated in the jejunum-ileum or right colon) who are candidates to receive 177Lu-Dotatate targeted radioligand therapy (RLT) and SSA. Patients with a large SRI+ mesenteric mass with abdominal-dominant disease judged by the investigator to be a midgut NET will also be eligible. 2. Ki-67 index ≤ 20%. 3. Disease progression per RECIST v1.1 within 36 months prior to study entry, 4. Patients may be treatment naïve (first-line) or have received prior systemic therapy except for any type of prior RLT (not restricted to 177Lu-Dotatate). 5. In somatostatin receptor (SSTR) imaging all RECIST v1.1 evaluable target lesions and non-target lesions need to be SSTR positive (SSTR+) as defined by equal or above the liver uptake (this includes lesions of at least 10 mm in diameter in CT or MRI). If an FDG PET is performed (not mandatory), all FDG PET positive lesions should also be somatostatin receptor positive in SSRT imaging (see guidance Appendix 10). 6. Measurable disease according to RECIST v1.1 criteria (Appendix 3) 7. Adequate organ function (hematological, renal and liver) based upon meeting all of the following laboratory criteria: * Neutrophil count (ANC) ≥ 2.000/mm3 * Platelet count ≥ 75 × 109/L * Hemoglobin ≥ 8 g/dL * Serum bilirubin ≤ 3.0 × upper limit of normal (ULN) or ≤ 3 × ULN for subjects with Gilbert's disease * Serum albumin \