18f-Psma Pet/Ct in the Multimodal Assessment of Metastatic Gastric Adenocarcinoma: A Case Report

The expression of Prostate Specific Membrane Antigen (PSMA) in the neovascular endothelium of non-prostatic tumors has presented new diagnostic perspectives. This report describes a young female patient with metastasis from gastric adenocarcinoma who underwent 18F-PSMA PET/CT during staging. A 42-year-old female with no prior oncologic history was diagnosed with metastatic gastric adenocarcinoma (cT4bN3M1). As part of an institutional clinical trial, she underwent 18F-FDG and 18F-PSMA PET/CT before treatment initiation. Imaging revealed central nervous system (CNS) involvement, non-regional lymphadenopathy, bone metastasis and muscle implants. In the primary tumor, 18F-FDG uptake was higher than 18F-PSMA (SUVmax 23.5 vs. 6.4). A 1.5 cm brain metastasis in the left frontal lobe showed substantial uptake in both studies (SUV max 9.1 for PSMA vs. 15.4 for FDG). Notably, 18F-PSMA exclusively identified additional focal areas in the right frontal and temporal lobes (SUV max 9.2), further imaging studies are pending. Additionally, a T6 vertebral lesion (SUVmax 4.8) was present in the PSMA study and was occult on 18F-FDG PET/CT. The patient was referred for CNS radiotherapy and initiated palliative chemotherapy with capecitabine and oxaliplatin. The clinical utility of PSMA PET/CT in gastric cancer remains poorly explored in the literature. In this case, PSMA PET/CT demonstrated significant uptake in CNS and bone lesions, suggesting sensitivity for detecting specific metastatic sites through tumor neovasculature imaging. 18F-PSMA PET/CT represents a promising diagnostic tool in non-prostate malignancies and may provide incremental diagnostic value when used in conjunction with 18F-FDG PET/CT. Further clinical trials investigating the role of PSMA-targeting tracers in gastrointestinal cancers are warranted.