To evaluate the potential usefulness of 68Ga-NK224 positron emission tomography/computed tomography (PET/CT) for the evaluation of PD-L1 expression in primary and/or metastatic tumors, compared with histopathological results.

Participants with cancer underwent 68Ga-NK224 PET/CT for an initial assessment. Tumor uptake was quantified by the maximum standard uptake value (SUVmax) and mean SUV (SUVmean). In addition, the PD-L1 expression of lesions was confirmed by histopathological analyzing. The quantitative parameters of 68Ga-NK224 PET/CT were compared with histopathological result to evaluate the diagnostic efficacy.

Inclusion Criteria:

• (i) adult patients (aged 18 years or order);
• (ii) patients with newly diagnosed or previously treated malignant tumors (supporting evidence may include magnetic resonance imaging (MRI), CT, tumor markers and pathology report);
• (iii) patients who had scheduled 68Ga-NK224 PET/CT scans;
• (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 newly diagnosed or previously treated malignant tumors (supporting evidence may include magnetic resonance imaging (MRI), CT, tumor markers and pathology report); (iii) patients who had scheduled 68Ga-NK224 PET/CT scans; (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.