Validation of Postoperative Angiofibroma Radionuclide Imaging Study (PARIS) Protocol Using PSMA PET/CT-A Proof of Concept Study.

OBJECTIVES: Juvenile nasopharyngeal angiofibroma (JNA) expresses prostate-specific membrane antigen (PSMA), and PSMA PET/CT scan may be used for its imaging. Also, the precise diagnosis of residual/recurrent JNA after surgical treatment remains difficult with conventional contrast MRI and/or CT; functional imaging with PSMA PET/CT promises greater accuracy in the detection or exclusion of recurrent/residual JNA.

PATIENTS AND METHODS: In this prospective study, 22 postoperative JNA patients who underwent a PSMA PET/CT scan both preoperatively and postoperatively from January 2018 to September 2020 were included. All patients underwent a low-dose head and neck spot PET/CT imaging. Abnormal postcontrast enhancement of a definite lesion was considered residual/recurrent tumor in contrast-enhanced MRI (CEMRI). In PSMA PET/CT, any abnormal uptake apart from physiological sites in the head and neck was considered as residual lesions. Radiological results were categorized as negative, suspicious for residual lesions, or definite residual/recurrent tumors. PSMA PET/CT findings were considered as the radiological standard, and patients were managed accordingly. The sensitivity, specificity, positive predictive value, and negative predictive value were separately calculated for CEMRI and PSMA PET/CT for diagnosing residual lesions.

RESULTS: On postoperative CEMRI evaluation, 12 patients had residual tumors, 2 had normal suspicious scans, and 8 had normal postoperative scans. On PSMA PET/CT, only 7 patients had residual tumors and 15 had normal postoperative scans. In 1 patient with a residual tumor on both scans, a discrepancy was noted concerning tumor extent, and PSMA PET/CT accurately mapped the tumor. The sensitivity, specificity, positive predictive value, and negative predictive value of CEMRI were 100%, 53.33%, 41.67%, and 100%, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of PSMA PET/CT were 100% for all parameters.

CONCLUSIONS: Because CEMRI is oversensitive and less specific compared with PSMA PET/CT, Postoperative Angiofibroma Radionuclide Imaging Study (PARIS) protocol should be used always. In residual tumors, PSMA PET/CT has an outright advantage over CEMRI in the diagnosis, tumor mapping, decision making, planning stereotactic radiation, and aiding in future follow-ups.