Purpose of study: 18F-FDG PET/CT plays a major role in diagnosis and staging of head and neck cancer; however, FDG has lower uptake in adenoid cystic carcinoma (AdCC). Prostate-specific membrane antigen (PSMA) expression is found to be associated with endothelial cells or tumor neovasculature in malignant AdCC and salivary duct carcinoma. Thus, present study is aimed to compare the role of 68Ga-PSMA and 18F-FDG PET/CT in patients with primary and/or metastatic AdCC.
Materials and methods: Histopathologically proven AdCC patients were intravenously injected with 370 MBq (10 mCi) of 18F-FDG and 111-185 MBq (3-5 mCi) of 68Ga-PSMA. Images were acquired at 60 and 45 minutes postinjection for 18F-FDG and 68Ga-PSMA, respectively, on dedicated PET/CT scanners. Visual and semiquantitative analyses of PSMA expression in regional and metastatic sites were performed by 2 experienced nuclear medicine physicians.
Results: Seventeen patients (7 men, 10 women) having mean age of 44 ± 14.19 years were prospectively included in the study. Of 17 patients, FDG PET/CT was performed in only 14 (82%) patients. PSMA and FDG uptakes were seen at the primary site in 16 (94%) and 13 (93%) patients, respectively, whereas 1 patient was postradical tumor excision. Lung lesions (n = 7) and lymph nodes (n = 5) were detected on both FDG and PSMA PET scans. However, cerebellar and meningeal metastasis (n = 1, 6%) and bony lesions (n = 2, 12%) were detected only on PSMA PET/CT but not visualized on FDG PET/CT scan.
Conclusions: PSMA may have theranostic importance in unresectable or metastatic AdCC, besides having a role in staging/restaging.
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