Chemoimmunotherapy + SFRT + Deep Hyperthermia for Biliary Tract Cancer

This study is being done to see if the investigators can improve the outcome of patients with biliary tract cancer that do not qualify for surgery. This study will compare the effects, good and/or bad, of using a combination of standard of care chemoimmunotherapy, with the addition of radiation and deep hyperthermia. In this study, participants will be receiving standard of care chemoimmunotherapy (gemcitabine, cisplatin, and durvalumab), radiation (spatially fractionated radiation therapy), and deep hyperthermia. Chemoimmunotherapy Chemoimmunotherapy is when chemotherapy drugs are combined with immunotherapy drugs. Chemotherapy uses different drugs to kill or slow the growth of cancer cells, whereas immunotherapy drugs are used to help the immune system attack cancer cells. For this study, the drugs Gemcitabine, Cisplatin, and Durvalumab will be used. Chemoimmunotherapy will be delivered over 4 cycles for this study and can continue longer if the treating physician decides this is appropriate. Each cycle will last 3 weeks. Spatially fractionated radiation therapy (SFRT) SFRT is a form of radiation therapy that gives a single large dose of radiation to large tumors or tumors that do not qualify for surgery. This is not a standard type of treatment for people with this diagnosis. For this study, participants will be receiving radiation once on day 1 of the second chemoimmunotherapy cycle. Deep Hyperthermia (HT) Hyperthermia is used in combination with chemoimmunotherapy and radiation treatment in this study. Hyperthermia has the potential to make both chemotherapy and radiation treatments more effective. For this study, participants will receive HT three times: on the first day of cycles 2, 3, and 4 of chemoimmunotherapy.