Precision Radiotherapy Using MR-linac for Pancreatic Neuroendocrine Tumours in MEN1 Patients

Patients with the Multiple Endocrine Neoplasia type 1 (MEN1) syndrome are genetically predisposed for developping multiple pancreatic neuro-endocrine tumours (pNET). The management of small (pNET) in both MEN1 and sporadic cases, pose a major clinical challenge. At present, pancreatic surgery is the only curative treatment but it is associated with high morbidity. To reduce the morbidity ascosiated with surgery and thereby potentially improve quality of life for MEN1 patients introduction of less invasive techniques for treatment of pNET is important. High-dose-high precision MR-guided radiotherapy (MRgRT) holds promise as a new less invasive treatment option for pNET. The aim of this study is to assess efficiacy and safety of MRgRT for treatment of pNET in MEN1 patients.

All patients meeting the following criteria will be assessed for in the tumour board: * lesions measuring between 2cm and 3cm. * pNET lesions with a size between 1.0 and 2.0 cm and moderate growth of the lesion (2-4 mm/ year) on sequential follow-up scans. * pNET lesions with a size between 1.0 and 2.0 cm and minimal growth of the lesion (1 mm/ year) reconfirmed on 3 or more sequential follow-up scans. * Patients with in situ remaining 1.0 - 2.0 cm lesions after previous resection of a larger lesion. All patients with such lesion and an indication for surgery are considered eligible for participation in the PRIME study. Exclusion Criteria: * Suspected malignant pNET as per the tumour board assessment, including the criteria: * pNET lesions of more than 3 cm in size * rapid growth of pNET lesions with more than 4mm per year * Symptomatic pNET because of hormone production, with the exception of gastrinomas which are located in the submucosa of the duodenum * concurrent treatment with a somatostatin analog * concurrent treatment with chemotherapy * peptide receptor radionuclide therapy in the past 12 months * history of radiotherapy in the upper abdominal region * MRI contraindications as per usual clinical care, such as claustrophobia and metal or electronic implants not compatible with MRI. * Pregnancy * (Other) metastatic disease * WHO performance score 3-4