Comparison of Prostate-Specific Membrane Antigen PET/CT and Contrast-Enhanced Magnetic Resonance Imaging in Follow-up Assessment of Juvenile Nasal Angiofibroma-A Novel Pilot Study

Alok Thakar, Pirabu Sakthivel, Sreedharan Thankarajan Arunraj, Ashu Seith Bhalla, Aanchal Kakkar, Rakesh Kumar, Rakesh Kumar
Clinical Nuclear Medicine 2020 October 16

PURPOSE/BACKGROUND: The specific identification of residual/recurrent juvenile nasal angiofibroma (JNA) following surgical treatment remains difficult. Contrast MRI and CT may not enable the differentiation of tumor from postsurgical reparative tissue. Functional imaging with prostate-specific membrane antigen (PSMA) PET/CT targeting tumor-associated neovasculature has recently demonstrated universal positive uptake in primary JNA and offers promise of greater accuracy in the detection or exclusion of recurrent/residual JNA.

METHODS: In this prospective study, 18 postsurgical JNA patients with high suspicion for residual disease evinced by follow-up MR scan, or nasal endoscopy, or recent epistaxis during September 2018-November 2019 were included. All patients underwent head and neck spot PSMA PET/CT imaging. Postcontrast enhancement of a definite lesion was considered as a criterion for 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, and residual/recurrent tumors. Any discrepancy between CEMRI and PSMA was resolved by surgical biopsies. The sensitivity, specificity, and positive and negative predictive values were separately calculated for CEMRI and PSMA PET/CT for diagnosing residual lesions. The interrater agreement κ value was also calculated.

RESULTS: On CEMRI evaluation, 14 of 18 patients had residual tumors, 2 had suspicious residual lesions, and 2 had normal postoperative scans. On PSMA PET/CT, 12 of 18 patients had residual tumors, and 6 had normal negative scans. Surgical biopsy in all 4 discordant cases was negative for tumors and revealed only fibrosis. In 1 patient with residual tumor on both scans, discrepancy was noted with regard to tumor extent demonstrated by the 2 scans, and further surgical excision confirmed the imaging findings of PSMA PET/CT as accurate. The sensitivity, specificity, and positive and negative predictive values of CEMRI were 100%, 33.33%, and 75% and 100%, respectively. The sensitivity, specificity, and positive and negative predictive values of PSMA PET/CT were 100% for all parameters. The interrater agreement between the 2 tests (κ) is 0.5 (95% confidence interval, 0.19-0.81).

CONCLUSIONS: The Ga-PSMA PET/CT is noted as more specific than the current standard of CEMRI in the identification of residual/recurrent JNA. It is the first radionuclide imaging scan that has found application in postoperative assessment of JNA.

TRIAL REGISTRATION: Clinical Trials Registry of India (CTRI/2018/08/015479).

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