The goal of this clinical trial is to evaluate the clinical use of [68Ga]Ga-FAPI-46 PET (positron emission tomography)/CT (computed tomography) imaging in patients with pancreatic or bile duct cancer. The study consists of three parts and patients can only participate in one part of the study.

The main questions the study aims to answer are:

• In part A: What is the best timing and scanprotocol of a [68Ga]Ga-FAPI-46 PET/CT scan?
• In part B: Are the results of the simplified scan protocol repeatable?
• In part C: What is the accuracy of [68Ga]Ga-FAPI-46 PET/CT to detect pancreatic cancer and is it able to detect the effect of chemotherapy on pancreatic cancer lesions?

Participants in this study will be asked to undergo the following:

• In part A: participants will undergo 1 [68Ga]Ga-FAPI-46 PET/CT scan and will have 2 venous canullas and 1 arterial cannula placed.
• In part B: participants will undergo 2 [68Ga]Ga-FAPI-46 PET/CT scans and will have a venous cannula placed for each scan.
• In part C: participants will undergo 2 [68Ga]Ga-FAPI-46 PET/CT scans and will have a venous cannula placed for each scan.

Pancreaticobiliary cancer patients have a dismal prognosis. Therefore, patient stratification for the proper primary treatment is crucial to prevent unnecessary surgery and opens up the opportunity for novel (multimodal) treatment. Unfortunately, conventional imaging modalities are not sensitive enough to detect small tumor lesions or differentiate between benign and malignant tissue after neoadjuvant therapy. Tumor-specific imaging, using PET/CT imaging, can identify tumor tissue more accurately and therefore can improve lesion detection and patient stratification. Fibroblast activation protein (FAP) shows promise as a target to identify pancreaticobiliary cancers, lymph node metastases, and residual disease after neoadjuvant therapy. The FAP targeted inhibitor (FAPI) is developed to target FAP and has been labelled to the Gallium-68 (68Ga) radioisotope, resulting in the [68Ga]Ga-FAPI-46 tracer.

This study will be a three part monocenter study focusing on the clinical evaluation of [68Ga]Ga-FAPI-46.

• In part A, the pharmacokinetics of this tracer will be studied and the simplified method(s) to quantify tracer uptake will be validated.
• In part B, a test-retest study will be performed to assess the repeatability of these simplified quantitative methods.
• In part C, the sensitivity and feasibility of therapy response monitoring will be investigated.

Inclusion Criteria:

• Patients aged 18 years or older.
• Before patient registration, written informed consent must be given according to ICH/GCP, and national/local regulations.
• Additional Part A: patients with pancreaticobiliary cancer (pancreatic, intra- or extrahepatic cholangiocarcinoma) and a tumor size of >20mm on CT.
• Additional Part B: patients with primary pancreatic (or pancreaticobiliary) cancer (depending on the results of part A) and a tumor size of >20mm on CT. No treatment may be given in between the two scans.
• Additional Part C: patients with pathologically proven pancreatic ductal adenocarcinoma, eligible for neoadjuvant therapy before surgical resection.

Exclusion Criteria:

• Women who are pregnant and/or lactating.
• Medical or psychiatric conditions that compromise the patient's ability to give informed consent. Presence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule.
• Impaired renal function (creatinine clearance <60 mL/min according to the Cockcroft-Gault equation.
• Leucocytes (WBC) ≤3.0 x 10^9/l
• Platelets ≤ 100 x 10^9 /l
• Hemoglobin ≤ 6 mmol/l
• Known hypersensitivity to drugs comparative to [68Ga]Ga-FAPI-46, or any of the excipients of [68Ga]Ga-FAPI-46.
• Inability to undergo PET/CT scanning (e.g. claustrophobia, weight limits or inability to tolerate lying for the duration of a PET/CT scan (~90 min)).

Additional Part A:

• Contra-indication for arterial cannula (e.g. inadequate circulation of extremity, positive Allen test, severe atherosclerosis, coagulant disorder (INR >1.4 or APTT >50)).

Additional Part C:

• Not eligible for surgery after neoadjuvant chemotherapy.
• If based on the first FAPI-46 PET/CT, there is a suspicion of metastatic disease the images will be discussed in the multidisciplinary meeting and one additional imaging modality (and a biopsy, if this would lead to a change of treatment strategy) can be used to confirm the suspicion. If metastatic disease is confirmed the patient will be excluded.

The IPD will be shared anonymously only of the participants who have given informed consent to share their data for other research proposes.

At the time of journal article publication.

Research data may be provided upon a reasonable request with necessary privacy provisions and only data form participants who have given informed consent for the use data for other research.