The goal of this clinical trial is to learn if [68Ga]Ga-FAPI-46 Total Body PET/CT can diagnose patients suffering from gastroesophageal cancer and pancreatic cancer. The investigators hope that [68Ga]Ga-FAPI-46 Total Body PET/CT can improve staging and treatment evaluation for these patient groups.

The main questions the trial aims to answer are:

• Is [68Ga]Ga-FAPI-46 Total Body PET/CT better at diagnosing metastatic disease in the abdomen compared other imaging modalities?
• Can [68Ga]Ga-FAPI-46 Total Body PET/CT produce accurate images in less than 30 min?

Researchers will examine three different patient groups:

Group A) patients with pancreatic cancer, who are referred to surgery. Group B1) patients with gastroesophageal cancer, who are referred to diagnostic surgery (laparoscopy).

Group B2) a subgroup of gastroesophageal cancer patients, with a specific subtype cancer (signet ring cell carcinoma or poorly cohesive carcinoma), who are referred to oncological treatment.

Participants will undergo:

• One [68Ga]Ga-FAPI Total Body PET/CT before surgery (Group A), or before laparoscopy (group B1), or before oncological treatment (Group B2).
• Participants in group B2 will also undergo a second [68Ga]Ga-FAPI-46 Total Body PET/CT during treatment with chemotherapy.
• All participants will fill out one questionnaire.
• Researchers will follow the patients after the scans for 1 year.

Inclusion criteria for group A

1. Male or female, over 18 years old
2. Patients with suspected pancreatic cancer based on morphological findings on standard imaging
3. CT or MRI or [18F]FDG PET/CT evaluated on MDT with no initial sign of distant metastases
4. Subjects must have been considered suitable for curative surgery at the time of the referral
5. Subjects must be able to read and understand the patient information in Danish to give informed consent

Inclusion criteria for group B1

1. Male or female over 18 years old
2. Histological verified carcinoma from the lower esophagus, GEJ, or stomach
3. Subjects must be considered operable and resectable at the time of referral for MDT
4. Subjects must be able to read and understand the patient information in Danish to give informed consent

Inclusion criteria for group B2

1. Male or female over 18 years old
2. Histological verified SRCC or PCC from the lower esophagus, GEJ, or stomach
3. Subjects with localized disease assigned to perioperative chemotherapy or subjects with metastatic disease assigned to palliative systemic treatment.
4. Subjects must be able to read and understand the patient information in Danish to give informed consent

Exclusion Criteria:

1. Pregnancy or lactation
2. Weight more than the maximum limit of a PET/CT-scanner bed (140 kg)
3. History of allergic reaction due to compounds similar to the chemical composition of [68Ga]Ga-FAPI-46