Adaptive Radiation for Locally Advanced Unresectable Pancreatic Cancer

The goal of this clinical trial is to learn if Adaptive Radiation Therapy (ART) is safe and effective in treating patients with locally advanced pancreatic cancer. The main questions the study aims to answer are: * Can ART improve how well radiation therapy targets the most aggressive cancer cells, while protecting the healthy tissue around the tumor? * Can ART help reduce the side effects that participants may experience during treatment? Participants will: * Undergo CT scans to plan the exact location of the radiation treatment. During this process, 1-3 small markers may be placed in or near the tumor to help with the planning. * Have a tumor biopsy, which involves taking a small sample of tissue from the cancer. * Receive 5 radiation treatments every other day over a 2-week period. * Provide blood samples before, during, and after your radiation treatment.