Early Feasibility Clinical Investigation to Assess YntraDose™ as a Neoadjuvant Treatment for LA-PDAC

The goal of this clinical investigation is to learn if a new type of radiotherapy works to treat pancreatic cancer that cannot be removed surgically. It will also learn about the safety of the new treatment when combined with chemotherapy. The treatment involves injecting a radioactive implant (medical device) directly into the pancreatic tumour on one occasion only. The main questions it aims to answer are: * Is the new treatment safe and tolerable when used in combination with standard of care chemotherapy. * Is it feasible to inject the new treatment directly into a patient's pancreatic tumour. * What is the impact of this new treatment on a patient's quality of life including a pain evaluation. * To assess how the pancreatic tumour responds to the treatment during the 3 month follow up. Participants will: * Participate in the research study for approximately 7 months and will receive standard of care chemotherapy throughout their participation. * Participants will initially receive standard of care chemotherapy which will be stopped after 2 months to reassess the tumor by a multidisciplinary tumor board. Chemotherapy will resume and the test device will be administered between chemotherapy treatments. The new treatment involves a single injection of the radioactive implant directly into the pancreatic tumour. Following treatment, the participant's standard of care chemotherapy will resume. * Participants will attend follow up visits over 3 months. * Participants will visit the clinic on 8 separate occasions and on one occasions, will remain in hospital for 2 nights/3 days to receive treatment with the new radiotherapy device and to monitor for safety. * Participants will complete questionnaires to check how the treatment is affecting their daily lives and pain levels. * Participants will undergo different types of imaging (scans) such as CT, MRI. * Participants will have bloods and urine taken to monitor safety.