Glutamine is a crucial nutrient for cancer cell growth, and its metabolism is frequently dysregulated in malignancies. 18F-FGln is a PET tracer that targets this altered glutamine metabolism. However, there are currently limited studies on the diagnostic value of 18F-FGln PET/CT in various types of cancer. Therefore, this prospective study was conducted to investigate the value of 18F-FGln PET/CT in patients with various types of malignant tumors.

Glutamine is the most abundant amino acid in plasma and a key metabolic fuel for cancer cells. The process of glutaminolysis supports tumor growth by providing carbon, nitrogen, and energy. PET imaging of glutamine flux using the radiotracer 18F-(2S,4R)-4-fluoroglutamine (18F-FGln) offers a novel approach to visualize a hallmark of cancer metabolism in vivo. Early human trials have demonstrated the safety and feasibility of 18F-FGln PET, showing uptake in various cancer types. More recent studies have shown its potential in specific applications, such as grading cerebral gliomas and guiding brain tumor biopsies. However, there are currently limited studies on the diagnostic value of 18F-FGln PET/CT across a broad spectrum of cancer types. Therefore, this prospective study was conducted to evaluate the diagnostic performance of 18F-FGln PET/CT in patients with various types of malignant tumors, using histopathological diagnosis as the gold standard.

Inclusion Criteria:

1. Patients with clinical suspicion or exclusion of primary or recurrent malignant tumors (such as glioma of the brain, liver cancer, gastric cancer, duodenal cancer, colorectal cancer, ovarian cancer, etc., where 18F-FDG is prone to false negatives and false positives)
2. Patients undergoing tumor staging or evaluating treatment effect using 18F-FDG PET/CT or 18F-FGln PET/CT to determine the most appropriate treatment strategy
3. Patients without other tumor history
4. Patients with good compliance, providing informed consent, and able to follow the research protocol

Exclusion Criteria:

1. pregnant or lactating patients or patients under 18 years old
2. the subjects and their parents or legal representatives are unable or unwilling to provide written informed consent;
3. patients with poor compliance, unable to tolerate or cooperate with PET/CT examinations.
4. those who have undergone gastrointestinal barium meal examination within one week;
5. other situations where the investigators consider it inappropriate for the subjects to participate in this clinical trial

This study will include patients from the Affiliated Cancer Hospital & Institute of Guangzhou Medical University who underwent an 18F-FGln PET/CT scan between October 2025 and January 2028 . Eligible participants are adult patients aged 18 to 70 years with suspected or histopathologically confirmed malignant tumors. Patients with non-malignant lesions, pregnant women, and those with incomplete medical records or missing histopathological reference standards will be excluded. Data will be collected by reviewing the institutional medical records and PET/CT imaging database.