TRACE-BTC. Relation of Biomarkers and Patients Reported Quality of Life to Outcomes in Patients With Biliary Tract Cancer: a Real- World Cohort

Purpose of the Study: Bile duct cancers are rare and aggressive. About 250 new cases are diagnosed each year in Denmark. These cancers are difficult to detect early, so only about 20% of patients can have surgery when diagnosed. Even after surgery, the cancer often returns, and chemotherapy only slightly reduces the risk of relapse. For patients who cannot have surgery, treatments such as chemotherapy (sometimes combined with immunotherapy) can relieve symptoms and extend life, but their effect is limited. A small number of patients have specific genetic changes in their cancer that can be treated with targeted medicines. Currently, doctors cannot predict which patients will benefit from treatment. Standard monitoring methods like CT scans are expensive, inconvenient, and sometimes unreliable because bile ducts are hard to see clearly on scans. Blood tests that detect cancer DNA in the blood (called circulating tumor DNA or ctDNA) and other biological markers may be a better way to monitor the disease and adjust treatment. These tests could help detect cancer recurrence earlier and determine whether treatment is working. Measuring patients' quality of life and symptoms over time may also help predict treatment benefit and evaluate effectiveness. The goal of this study is to: * Investigate how biomarkers, including ctDNA, can predict disease course, detect relapse, and monitor treatment response. * Identify the best way to measure ctDNA in patients with bile duct cancer. * Examine whether patients' own reports of quality of life and symptoms can help assess treatment effect and prognosis. Study Design and Procedures: This is a prospective cohort study focusing on blood biomarkers and patient-reported symptoms and quality of life. Participants agree to provide blood samples: * Before treatment * During treatment * During follow-up Each sample involves up to 40 ml of blood, with a maximum of 20 samples per patient. The blood will be analyzed for: * ctDNA a