Stereotactic Body Radiotherapy (SBRT) Induced Pancreatic Atrophy for Prevention of Post Operative Pancreatic Fistulae (POPF) After Pancreatoduodenectomy in Very High-Risk Patients (STEREOPANC)

Inclusion Criteria: * Patients scheduled to undergo pancreatoduodenectomy for any indication but no pancreatic duct occlusion * Pancreatic duct diameter ≤ 3 millimetres, measured on the diagnostic CT scan (at the level of the portomesenteric vein, at the pancreatic neck, the future anastomotic site). * WHO-ECOG performance status 0,1 or 2. * Ability to undergo stereotactic radiotherapy and surgery. * Age ≥ 18 years. * Good understanding of the oral and written patient information provided. * Written informed consen Exclusion Criteria: * Patients undergoing pancreatoduodenectomy with dilated duct \> 3mm * Patients with (a history of) chronic pancreatitis * Patients with contraindications to SBRT * Prior radiotherapy to the gross target area * Pregnancy * Connective tissue disorder (systemic lupus erythematosus, scleroderma etc) * Radiosensitizing medication that cannot be safely paused (methotrexate, post-transplant medications etc.)¬¬ * Inflammatory bowel disease * Inherited radiation hypersensitivity syndrome (ataxia-teleangiectasia mutation, ATM) * Inability to perform a light inspiration breath hold repeatedly (8-10 times 20s breath hold) * Severe allergy to contrast agents