CisPlatin plUs Gemcitabine and Nabpaclitaxel (GAP) as pReoperative Chemotherapy Versus Immediate Resection in patIents With resecTable BiliarY Tract Cancers (BTC) at High Risk for Recurrence

Inclusion Criteria: 1. Patient able and willing to provide written informed consent and to comply with the study protocol and with the planned surgical procedures. 2. Female and male patients ≥18 years and \<75 years. 3. Histologically or cytologically confirmed non metastatic resectable carcinoma of biliary tract (BTC), including gallbladder carcinoma (GBC), intrahepatic, periperihilar or distal Cholangiocarcinoma (CCA). Mixed tumor entities with hepatocellular carcinoma and ampullary cancers are excluded. 4. Availability of a tumoral sample 5. ECOG performance status of 0-1. 6. No prior tumor resection for BTC. 7. Exclusion of distant metastases by CT or MRI of abdomen, pelvis, and thorax and PET scan. 8. Technically resectable BTC as per local Multidisciplinary Team (MDT) assessment, including a core team with at least one medical oncologist, one surgeon, one radiologist, one endoscopist/gastroenterologist and one pathologist, all with expertise \> 3 years on biliary tract cancer and hepatobiliary oncology. 9. High risk for recurrence defined as the presence of at least one of the following risk features, as evaluated at baseline (pre-surgery): 1. For cholangiocarcinoma: * Suspected or definite locoregional lymph node involvement (at least one of the following): * positive FNA cytology (obtained by EUS). * positive locoregional lymph nodes at PET-CT. * suspected positive locoregional lymph nodes at imaging (CT or MRI scan) according to local MDT discussion (eg. short axis \> 1.5 cm, contrast enhancement uptake, round shape, restriction at DWI). * Macrovascular invasion at preoperative CT scan. * Expected R1 resection due to proximity to major intrahepatic vascular and biliary structures. * For iCCA, presence of satellitosis or multifocal disease or radiological suspicion of tumoral diaphragmatic adhesion. * For iCCA, size of the liver lesion \>5 cm. * For eCCA, size of the primary lesion \> 3cm. * Ca19.9 \>100 U/mL. 2. For GBC: * Incidentally Detected Gallbladder Carcinoma (IGBC) after simple cholecystectomy with indication for radical second surgery (\>pT2) or newly diagnosed GBC. 10. Estimated life expectancy \> 3 months. 11. Adequate baseline hematologic function characterized by the following at screening: 1. ANC ≥ 1.5 × 109/L 2. platelets ≥ 100 × 109/L 3. hemoglobin ≥ 9 g/dl. Note: prior transfusions for patients with low hemoglobin are allowed. 12. Adequate liver function characterized by the following at screening: 1. Serum total bilirubin ≤ 1.5 × ULN and \< 2 mg/dL. Note: Subjects with Serum total bilirubin ≥ 1.5 × ULN and conjugated bilirubin ≤ ULN or \< 40% of total bilirubin are allowed. 2. Serum transaminases (AST and/or ALT) \< 3 x ULN. 13. Adequate renal function, i.e. serum creatinine ≤ 1.5 x institutional ULN and calculated by Cockroft-Gault formula or directly measured creatinine clearance ≥ 50 mL/min 14. Adequate coagulation functions as defined by International Normalized Ratio (INR) ≤ 1.5, and a partial thromboplastin time (PTT) ≤ 5 seconds above the ULN (unless receiving anticoagulation therapy). 15. No presence of complete dihydropyrimidine dehydrogenase (DPD) enzyme deficiency with DPYD gene testing mandatory at screening as per national guidelines 16. Females of childbearing potential must agree to remain abstinent (refrain from sexual intercourse) or use highly effective contraceptive methods, as defined in APPENDIX V of the full protocol, during the treatment period and for at least 7 months after the last administration of study treatments. 17. Males must agree to remain abstinent (refrain from sexual intercourse) or use highly effective contraceptive methods, as defined in APPENDIX V of the full protocol. 18. Negative serum pregnancy test within 7 days of starting study treatment in pre-menopausal women and women \<1 year after the onset of menopause. 19. A participant must agree not to donate eggs/sperm for future use for the purposes of assisted reproduction during the study and for a period of 7 months after receiving the last dose of study treatment. Female and male participants should consider preservation of eggs/sperm prior to study treatment as anti-cancer treatments may impair fertility. Exclusion Criteria: 1. Known allergy or hypersensitivity to any of the study drugs. 2. Any known additional malignancy that is progressing or requires active treatment, or history of other malignancy within 2 years of study entry except for curatively treated basal cell carcinoma of the skin, in situ carcinoma of the cervix, and prostate cancer. 3. Locally unresectable tumor according to local MDT (including radiological evidence suggesting inability to resect with curative intent whilst maintaining adequate vascular inflow and outflow, and sufficient future liver remnant). 4. Evidence of distant metastases at any site. 5. Tumors requiring multi-step surgical procedures such as two-stage hepatectomy or Associating Liver Partition and Portal vein Ligation for Staged hepatectomy (ALPPS) due to liver volumetry-based assessment of anticipated inadequate future liver remnant. 6. Cirrhosis at a level of Child-Pugh B (or worse) or cirrhosis (any degree) and a history of hepatic decompensation in the year before enrolment. 7. Know active uncontrolled hepatitis B or hepatitis C. Patients with a past or resolved HBV infection are eligible. Patients with chronic disease controlled by antiviral therapy or requiring prophylactic treatment are eligible. 8. Chronic or current active infectious disease requiring systemic antibiotics or antifungal treatment within 2 weeks prior to enrollment. 9. Known uncontrolled HIV infection. HIV-positive patients are eligible if their CD4+ cell count amounts to 300 cells per μL or more; HIV viral load must be undetectable per standard of care assay, and they must be compliant with antiretroviral treatment. 10. Pregnant or breast-feeding patient, or patient is planning to become pregnant within 7 months after the end of treatment. 11. Any other concurrent antineoplastic treatment including radiotherapy. 12. Previous or concurrent systemic (eg cytotoxic or targeted or other experimental drugs) therapy for BTC. 13. Prior surgery or locoregional therapy for BTC. 14. Severe or uncontrolled cardiovascular disease (congestive heart failure NYHA III or IV, unstable angina pectoris, history of myocardial infarction in the last three months, significant arrhythmia). 15. Presence of psychiatric disorder precluding understanding of information of trial related topics and giving informed consent. 16. Any serious underlying medical conditions (judged by the investigator), that could impair the ability of the patient to participate in the trial. 17. Presence of complete dihydropyrimidine dehydrogenase (DPD) enzyme deficiency with DPYD gene testing mandatory at screening as per national guidelines. 18. Lack of physical integrity of the upper gastrointestinal tract, malabsorption syndrome, or inability to take oral medication.