⁃ 1\. Patients diagnosed with unresectable BTC who meet any of the following:

• Patients who were deemed unamenable to curative resection at the initial diagnosis.

• Patients who relapsed after curative resection of BTC more than 6 months after the end of adjuvant therapy or after the date of surgery for patients who did not receive adjuvant therapy.

⁃ 2\. Patients who received first-line systemic therapy for unresectable BTC with the date of the first dose between May 1, 2022, and December 31, 2023. However, patients who received postoperative adjuvant therapy for BTC with R2 resection is not included.

⁃ 3\. Patients with ECOG performance status 0 or 1 on the most recent assessment date prior to first dose of first-line systemic therapy for unresectable BTC 4. Patients who provided written informed consent form (ICF), in cases where obtaining informed consent is not difficult, or for whom an appropriate opt-out approach was taken at the study site if obtaining informed consent is difficult.

⁃ 5\. Patients aged 18 years or older at the date of first dose of first-line systemic therapy for unresectable BTC.

⁃ 6\. Patients who started first-line systemic therapy with physician's expectation of 3 months or longer prognosis at the time of starting systemic therapy.