To evaluate the potential usefulness of 68Ga/18F-FAPI positron emission tomography/computed tomography (PET/CT) for the diagnosis of primary and metastatic lesions in various FAP-related disease patients.

Subjects with various FAP-related disease patients underwent 68Ga/18F-FAPI PET/CT either for an initial assessment or for recurrence detection. Lesions uptake was quantified by the maximum standard uptake value (SUVmax). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of 68Ga/18F-FAPI PET/CT were calculated.

Inclusion Criteria:

• (i) adult patients (aged 18 years or order); (ii) patients with suspected or new diagnosed or previously treated malignant tumors (supporting evidence may include MRI, CT, tumor markers and pathology report); (iii) patients who had scheduled FAPI PET/CT scan; (iv) patients who were able to provide informed consent (signed by participant, parent or legal representative) and assent according to the guidelines of the Clinical Research Ethics Committee.

Exclusion Criteria:

• (i) patients with non-malignant lesions; (ii) patients with pregnancy; (iii) the inability or unwillingness of the research participant, parent or legal representative to provide written informed consent.

(i) adult patients (aged 18 years or order); (ii) patients with suspected or new diagnosed or previously treated malignant tumors (supporting evidence may include MRI, CT, tumor markers and pathology report); (iii) patients who had scheduled FAPI PET/CT scan; (iv) patients who were able to provide informed consent (signed by participant, parent or legal representative) and assent according to the guidelines of the Clinical Research Ethics Committee.