Neoadjuvant Gemcitabine and Cisplatin in Combination With Perioperative Pembrolizumab Versus Upfront Surgery for Patients With Primary Resectable and Borderline Resectable Perihilar and Distal Cholangiocarcinoma

Inclusion Criteria:

* Histologically or cytologically confirmed resectable or borderline resectable pCCA and dCCA. These are all the patients considered candidates for upfront surgical exploration, with intent to resect, as confirmed by local MDT and the study expert panel also taking into consideration endoscopic and radiological findings. In cases where drainage is not required, patients with a disease highly suspicious for extrahepatic cholangiocarcinoma, as determined by the expert MDT, may be included without histological proof to prevent unnecessary post-ERCP complications.
* Successful drainage, in case of clinical significant bile duct obstruction.
* MidCCA inclusion in the NEODISCO-trial will be permitted and will be included according to the proposed type of resection.
* Male/female participants who are at least 18 years of age on the day of signing informed consent.
* Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1. Evaluation of ECOG is to be performed within 7 days prior to the first dose of study intervention.

Exclusion Criteria:

* Upfront "clearly" unresectable pCCA: circumferential unreconstructable vascular involvement of the FLR and/or insufficient FLR for potential radical resection. Insufficient FLR is defined as \<30% residual volume or a function \<2.7 min/m2. Patients considered borderline resectable but, by the discretion of the MDT, not a candidate for upfront exploration/resection, are considered ineligible for NEODISCO.
* Upfront clearly unresectable dCCA (following DPCG criteria).
* Patients with proven N2 lymph nodes (according to the AJCC 8th edition).
* PCCA eligible for liver transplantation.
* Intrahepatic cholangiocarcinoma with hilar involvement.
* Cancer suspicious for ampullary carcinoma (for instance involvement of papilla during endoscopy).
* Local recurrence following prior resection of eCCA (patients who develop local recurrence during the study are however not excluded).
* Patients with underlying liver diseases: PSC, untreated hepatitis, cirrhosis child-Pugh B, C.
* Previous malignancy unless no evidence of disease, or diagnosed more than 3 years before diagnosis of eCCA, or with a life expectancy of more than 5 years from date of inclusion.
* Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg, CTLA-4, OX-40, CD137).