In this prospective study, the investigators will use integrated PET/CT with the agent 68Ga-FAPI and conventional imaging agent 18F-FDG to explore the application value of FAP-targeted molecular imaging in the diagnosis and staging for oral cancer. This study also aims to explore the application value of FAPI imaging in evaluating treatment response for oral cancer.

Positron emission tomography (PET) molecular imaging provides a valuable method for the diagnosis, differential diagnosis and staging of various tumors. Cancer associated fibroblasts (CAFs) are the main components of tumor stroma, which are involved in tumor cell proliferation, invasion, metastasis and tumor angiogenesis, and play an important role in the occurrence and development of tumors. Fibroblast activation protein (FAP) is the most potential specific molecular marker of CAF, which is mainly expressed in stromal fibroblasts of epithelial tumors and is a potential molecular target for tumor diagnosis and treatment. Oral cancer is the most common type of malignant head and neck cancer, seriously endangering human health. Accurate delineation of the primary tumor, detection of regional nodal metastases, distant metastases and second primary tumors are important for determining the therapeutic strategy and prognosis of oral cancer. Currently, the molecular imaging agent most commonly used in clinical practice for oral cancer is 18F-fluoro-deoxy-glucose (18F-FDG). However, 18F-FDG exhibits some shortages. Inflammatory lesions and the surrounding normal tissue such as brain, tonsils and salivary glands show high uptake of 18F-FDG, often affecting the judgment of lesions.

Adult patients aged >18 years with clinically confirmed or highly suspected oral cancer will be enrolled. Participants receive paired baseline FDG and FAPI PET/CT to explore the diagnostic and staging value of FAPI PET in oral cancer. For resectable locally advanced cases receiving neoadjuvant therapy from oral and maxillofacial clinicians, a follow-up FAPI PET imaging will be performed after two cycles of treatment and before surgery to evaluate its application in treatment-response assessment. Ultimately, this study aims to comprehensively evaluate the clinical utility of FAPI PET/CT in oral cancer.

Inclusion Criteria:

1. Voluntary participation with signed informed consent;
2. Aged 18~70 years;
3. Clinically highly suspected oral cancer and recurrence after treatment (Newly diagnosed patients: Scheduled for surgery or neoadjuvant therapy followed by surgery);
4. Ability to complete baseline and follow-up PET/CT (Follow-up FAPI PET/CT applies only to locally advanced patients undergoing neoadjuvant therapy.).

Exclusion Criteria:

1. Pregnant or breastfeeding women, or women planning pregnancy during the trial period;
2. Known hypersensitivity to FAPI, FDG, or their components, or history of severe allergic reactions;
3. People with poor general condition, their heart, lung, liver, kidney and other important organ functions cannot tolerate surgery;
4. Before the injection of 18F-FDG, the fasting blood glucose level exceeded 11.0 mmol/L;
5. Claustrophobia or inability to tolerate PET/CT imaging (Those who cannot tolerate lying supine for 15~30 minutes.);
6. Participation in another interventional clinical trial within 30 days prior to enrollment, or planned participation during this study.

This study enrolls adults aged 18-70 years with clinically suspected or histopathologically confirmed oral cancer (primary or recurrent). Newly diagnosed patients are scheduled for surgery or neoadjuvant therapy, while recurrent cases require imaging/pathology confirmation. All participants must complete baseline FAPI PET/CT and FDG PET/CT for diagnostic/staging evaluation. Locally advanced patients receiving neoadjuvant therapy will undergo follow-up FAPI PET/CT for therapeutic response assessment. Exclusion criteria include pregnancy, severe allergies to FAPI/FDG, uncontrolled comorbidities, and recent participation in other interventional trials.