APPLICABILITY OF PSMA PET/CT IN THE EVALUATION OF ADENOID CYSTIC CARCINOMA

Adenoid Cystic Carcinoma (ACC) is a rare and aggressive tumor characterized by slow and indolent growth, high recurrence, high metastasis rates, and challenging early detection, and 18F-FDG PET/CT imaging has become essential for diagnosis, staging, and monitoring of it. In the last decade, the promising theranostic approach of 18F-PSMA PET/CT for prostate carcinoma has led to the evaluation of PSMA target with 18-Fluor (diagnostic) and 177-Lutetium (therapeutic) in ACC, whose cells overexpress this surface antigen. As it is a recent discovery, further studies are needed to evaluate the use of 18F-PSMA PET/CT to predict the prognosis and assess therapy response in ACC cases. Could 18F-PSMA PET/CT, compared to 18F-FDG PET/CT, be used as a diagnostic technique for ACC and, as a consequence, labeled PSMA be potentially a therapeutic resource for this cancer? Evaluate the applicability of 18F-PSMA PET/CT compared to 18F-FDG PET/CT in the management of ACC. Five patients (A, B, C, D, and E) diagnosed with ACC underwent 18F-FDG PET/CT and 18F-PSMA PET/CT (24-hour intervals, except by two cases), and the lesions uptakes were evaluated with both radiotracers. Patient A showed hypermetabolism only for 18F-FDG PET/CT at cervical lymph nodes; B exhibited an uptake substantially higher on 18F-FDG PET/CT at the primary lesion site, cervical lymph nodes, and lung (46 days between the exams and after treatment with doxorubicin); C and D showed similar uptake on both tracers: C at L5 vertebra and lung, and D at lung; E exhibited uptake of both tracers, in cervical lymph nodes with 18F-FDG, suggesting inflammation, and in the lung with 18F-PSMA. Preliminary data suggest similar uptake patterns for both tracers in ACC, with variations warranting further investigation. The study highlights the potential use of 18F-PSMA PET/CT in the diagnostic management of ACC, expanding its possible therapeutic application.