Multi-modal Characterisation of Gastroenteropancreatic Neuroendocrine Tumours (GEP-NETs) Treated With Targeted Radionuclide Therapy (TRT): Prospective Interventional Multicentre National Cohort

Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) are considered rare neoplasms. Their incidence has been increasing over the last few decades, and due to generally prolonged survival of patients, the prevalence of GEP-NETs is higher than the combined prevalence of other more common gastrointestinal cancers, including oesophageal cancers, gastric adenocarcinomas, and pancreatic adenocarcinomas. Prognosis is related to several factors and especially to liver tumour involvement.

Peptide Receptor Radionuclide Therapy (PRRT) is a targeted radionuclide therapy that has been used in the treatment of patients with GEP-NETs for over two decades. The molecular target for PRRT in NETs is the somatostatin receptor (SSTR), mainly the subtype 2, which is highly expressed in most of these tumours. The 177lu-DOTATATE, a radiolabelled somatostatin analog, has reached a wide use due to a combination of high anti-tumour activity and a low level of toxicity. 177Lu-DOTATATE was granted marketing authorisation by the European Medicines Agency in 2017 and by the Food and Drug Administration in 2018 for the treatment of GEP-NETs. Due to its high efficacy, it has become one of the most relevant therapeutic option for patients with inoperable and/or metastatic GEP-NETs.

Response evaluation - PRRT exerts antitumor effects based on radio-biological (DNA damages) and immunological mechanisms. While highly promising, patient stratification and early identification of responders are currently insufficient due to the lack of reliable biomarkers, either non-invasive or invasive. Furthermore, prior therapy-induced DNA damages may lead to tumour resistance, therefore reducing PRRT efficacy. Hence, the absence of a personalized treatment strategy is an unmet need for patients with GEP-NETs. This may result in survival disadvantage for non-responders, who could benefit otherwise from early treatment change, with expected more favourable outcomes.

Simultaneous PET-MRI: OPERANDI project proposes an innovative and holistic approach via PET-MRI guided therapy with somatostatin analogues (68Ga-DOTATOC). Our hypothesis is that simultaneous 68Ga-DOTATOC PET-MRI imaging provides more robust non-invasive predictive biomarkers than classical approach. This requires technological development of PET-MRI, with most methodological challenges being attenuation correction, reducing the impact of organ motion due to respiration and cardiac motion, and minimizing truncation and susceptibility artefacts.

A PET/MRI scan is a two-in-one exam that combines images from a positron emission tomography (PET) scan and a magnetic resonance imaging (MRI) scan. This new hybrid technology harnesses the strengths of PET and MRI to produce some of the most highly detailed images currently available. MRI scans use a strong (1.5 to 3T for clinical use) magnetic field to produce detailed morphologic images and some sequences provide functioning information (such as diffusion-weighted, dynamic contrast-enhanced, MR elastography sequence). PET scan use radiotracers according to the clinical indications to highlight metabolism or biological changes.

The most common radiotracer that has been used so far is fluorodeoxyglucose (FDG), which detects metabolically active malignant lesions. Gallium-68-labeled somatostatin analogues (including 68Ga DOTATOC) are differentiation markers in NETs and are a prerequisite for verifying sufficient SSTR2 expression and selecting patients for PRRT.

The OPERANDI project aims to address unmet clinical needs in the current management of GEP-NETs treated with PRRT by exploring new opportunities provided by imaging-based (AI algorithms) and data augmentation, simultaneous 68Ga-DOTATOC PET-MRI imaging, and novel approaches to increase patient selection and PRRT efficacy (genomic profiling, radiopotentiators, and new radionuclides). The study aim to identify predictive and early markers indicative of PRRT effectiveness based on a large prospective cohort of GEP-NET patients. This cohort will be used to uncover relevant predictive signatures within the morphological, functional, and molecular imaging data using novel imaging-based AI approaches with a new patient imaging pathway including simultaneous 68Ga-DOTATOC PET-MRI.