Clinical Applications of FAPI PET in Solid Tumors

This prospective study is designed to evaluate and compare the PET/CT or PET/MR imaging characteristics of two fibroblast activation protein (FAP)-targeted tracers-the novel tracer FAPI-RuiJ and the reference tracer FAPI-04-across a diverse range of solid tumors. All enrolled patients will undergo paired PET imaging with both FAPI-RuiJ and FAPI-04. For each tracer, semi-quantitative uptake parameters (including SUVmax, SUVmean, SUVpeak, tumor-to-background ratio [TBR]）will be measured and compared. Biodistribution characteristics of FAPI-RuiJ in normal organs will be assessed to determine its in vivo metabolic profile. Using histopathology or imaging follow-up as the reference standard, the diagnostic performance of FAPI-RuiJ PET will be compared with that of FAPI-04 PET, with evaluation metrics including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and area under the receiver operating characteristic curve (AUC). Correlation analyses will be performed between PET parameters and clinicopathological characteristics, including tumor markers, pathological subtype, and immunohistochemical markers.The study is expected to provide a novel molecular imaging tool to support early lesion detection, accurate staging, and recurrence surveillance in patients with solid tumors.

Inclusion criteria

• Age ≥ 18 years and ≤ 80 years, regardless of gender.
• Participants with suspected, confirmed, or suspected recurrent solid tumors.
• Participants who agree to participate in this clinical trial and provide written informed consent.
• Participants with good compliance, who commit to adhering to the study procedures and cooperate with the full study process.
• No plans for pregnancy within 6 months.

Exclusion criteria

• Patients with severe medical conditions that, in the investigator's opinion, make them unsuitable for participation in this clinical study, including but not limited to: severe cardiopulmonary insufficiency, severe bone marrow suppression, and severe hepatic or renal insufficiency.
• Patients with claustrophobia, severe psychiatric symptoms, or impaired consciousness that precludes cooperation with the examination procedures.
• Patients who have received any anti-tumor therapy during the interval between the two PET imaging sessions.
• Pregnant or breastfeeding women.
• Patients with poor compliance.