This study is testing how well two treatments work for biliary tract cancer (BTC), which affects tubes carrying bile from the liver. The first treatment uses rilvegostomig with standard cancer drugs gemcitabine and cisplatin. The second uses durvalumab with the same standard drugs. Rilvegostomig and durvalumab are special medicines designed to help the immune system fight cancer.

• The study is only for patients who have advanced BTC and haven't been treated for it yet.
• Participants should be able to have certain exams and tests, like CT or MRI scans, to measure the cancer.
• Patients cannot join if they have had previous chemotherapy for BTC or have certain health conditions, like autoimmune diseases.

Participants will receive treatment and be closely monitored by doctors. They won't be able to participate if they have other cancers or are on other cancer treatments. This research helps find better treatments and may offer new hope for those with BTC.