Radiation Therapy in Unresectable Gall Bladder Cancer

The goal of this clinical trial is to compare two treatment regimes, namely, systemic therapy (chemotherapy and/or immunotherapy) alone vs. systemic therapy and radiation therapy in patients with inoperable but localized gallbladder cancer. The main questions it aims to answer are: * Whether adding radiation therapy to systemic therapy improves overall survival? * What are the effects on other endpoints like cancer-free intervals, side effects, and quality of life? Participants will be randomly assigned to one of the two treatment regimes mentioned earlier by a computer-based program. Researchers will compare survival and quality of life outcomes between the two groups.