A Study of High Dose Radiation Therapy for Locally Advanced Pancreatic Cancer That Responded to Initial Chemotherapy Treatment

The goal of this clinical trial is to test the effect of high-dose radiation therapy after initial chemotherapy in patients with locally advanced pancreatic cancer. The main question it aims to answer is: • For patients with locally advanced pancreatic cancer that responded to initial chemotherapy (stayed stable or decreased in size), will high-dose RT (radiation therapy) contribute to improving treatment outcomes, enhancing quality of life, or increasing overall survival rates? Participants will: * Undergo an optional tumor biopsy. * Be treated with high dose radiation therapy. * Complete quality of life questionnaires. * Donate research blood samples.