177Lutetium-octreotate Treatment Prediction Using Multimodality Imaging in Refractory NETs

The purpose of this study is to determine if 68Gallium-octreotate and 18Fluorodesoxyglucose uptake, apparent diffusion coefficient and post 177Lu-octreotate SPECT/CT dosimetry are reliable predictors for lesion-by-lesion treatment outcome.

This is a feasibility study evaluating the use of 177Lutetium-octreotate in the treatment of advanced refractory Neuroendocrine Tumors. Objectives of the study: 1. Primary (on a lesion basis): To assess the value of the following parameters (obtained through functional and molecular imaging) for predicting the lesion-by-lesion PRRT treatment outcome: * 18FDG uptake on 18FDG PET/CT * 68Ga-octreotate uptake on 68Ga-octreotate PET/CT * Apparent diffusion coefficient on diffusion weighted MRI (for these 3 parameters, absolute values at baseline) * Tumor dosimetry on post 177Lu-octreotate SPECT/CT after each cycle. 2. Secondary (on a patient basis): To generate a patient-based response model based on the previously defined parameters. 3. Exploratory (on a lesion basis): To assess the value of the parameters mentioned in the primary objective for predicting the lesion-by-lesion PRRT treatment outcome: * absolute values of the three imaging parameters and their relative changes after each cycle; * serial tumor dosimetry on post-177Lu-octreotate SPECT/CT after each cycle. Treatment will consist of 177Lu-octreotate injections in fixed activities of 7,4 GigaBecqurel each, given 11-13 weeks apart, injected intravenously with simultaneous infusion of an amino acid solution. (Before amino acid nephroprotection, ondansetron, methylprednisolone and metoclopramid, are given intravenously in order to prevent nausea or vomiting). Approximately 30 min after the beginning of the amino acid solution, 177Lu-octreotate is co-infused over 15-30 minutes. The amino acid infusion is continued at the same rate for 3-5 more hours (total infusion lasts 4-6 hours). In total, 4 cycles (= injections of 177Lu-octreotate) are planned. However, the total number of administered cycles will be limited by critical organ (kidneys and bone marrow) threshold toxicities. Treatment efficacy will be assessed: * on a lesion-basis (change of longest transversal diameter). * on a patient-basis using Response Evaluation Criteria In Solid Tumors (RECIST) 1.1.