Investigation of Predictive Biomarkers in Patients With Advanced BTC Treated With Lenvatinib Plus Pembrolizumab

"* The collection of peripheral blood samples will follow the schedule below (20 cc per collection, up to 5 times):~* Before systemic therapy, at 3 weeks after starting systemic therapy (Cycle 1), at 6 weeks (Cycle 2)~* (If possible) at the time of confirmed partial response (1 time), and at the time of disease progression (1 time).~* Additional tumor tissue samples will be collected only if possible, according to the following schedule:~If the patient undergoes surgery or additional biopsy related to treatment (collected from preserved specimens)."