Background: Many cancer patients, especially those with pancreatic cancer, suffer from severe back/epigastric pain. Contemporary approaches (opioids, celiac blocks, systemic chemotherapy) are often inadequate. This clinical trial investigates a new approach in which high-dose radiation (radiosurgery) is focused on the retroperitoneal celiac plexus nerve bundle. Preliminary results from a single institution pilot trial NCT02356406 are promising: pain relief is substantial and side effects minimal. The main aim of the trial is to establish safety/efficacy in the setting of an international multicenter study. Exploratory analyses will examine the relationship between pain reduction and subjects’ quality-of-life, functionality, and caregiver burden. Methods: Eligibility criteria include a diagnosis of metastatic/unresectable malignancy, uncontrolled pain defined as ≥ 5 on 11-point BPI-SF scale despite analgesic use, typical retroperitoneal pain syndrome, prognosis > 8 weeks, ECOG 0-2, anatomical involvement of the celiac plexus (e.g. any pancreatic cancer, or any other cancer involving the celiac trunk). Exclusion criteria include previous upper abdo. radiation. The intervention consists of a single 25 Gy radiation fraction delivered to the celiac plexus, using anterolateral aspect of the aorta from the 12th thoracic to 2nd lumbar vertebral body as a surrogate structure. The primary tumour may be irradiated at physicians’ discretion. Dose-painting technique limits dose to organs at risk. Pain intensity will be measured using Brief Pain Inventory Short Form (BPI-SF), and quality of life with FACT-Hep. The primary endpoint is complete or partial pain response, defined as a decrease between the score immediately before treatment and 3 weeks’ post-treatment. A change of two or more on the BPI 11-point pain scale is defined as clinically significant. Secondary endpoints include other BPI pain endpoints, pain at 6 weeks, analgesic use, toxicity (CTCAE v4.03), quality of life and functional measures. Analgesia is not restricted. Expected accrual is 100 subjects over three years. Supported by Gateway for Cancer Research, additional support from Israel Cancer Association. Clinical trial information: NCT03323489