BEFAST Study, [68Ga]Ga-FAPI Total Body PET/CT for Better and Faster Imaging in Cancer

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.