Physiological PSMA Uptake in the Tubarial Salivary Glands and Its Implications in the PARIS Protocol-A First Study of Its Kind!

Abstract

Because prostate-specific membrane antigen (PSMA) expression is universal in juvenile nasal angiofibroma (JNA), PSMA PET/CT is commonly used in the postoperative setting using the postoperative angiofibroma radionuclide imaging study protocol. Our study aims to illustrate physiological PSMA ligand uptake distribution characteristics in the salivary glands, specifically the tubarial glands with tumor, to aid in accurate PSMA PET/CT analysis. Forty-three consecutive patients who underwent a dedicated head and neck spot PSMA PET/CT for JNA were evaluated retrospectively. PSMA SUVmax values in the tumor, tubarial, parotid, submandibular, and sublingual salivary glands were determined visually and quantitatively. All the tumors and the salivary glands showed increased tracer uptake. The median SUVmax ± SD ratios of the tumor, right and left tubarial gland, right and left parotid gland, right and left submandibular gland, and right and left sublingual gland were 2.7 ± 0.8 (range, 0.5-7.5), 3.8 ± 1.9 (range, 0.9-8.1), 4.7 ± 2.1 (range, 0.8-7.4), 9.5 ± 4.8 (range, 3.2-21.9), 9.2 ± 4.7 (range, 2.9-18.9), 10.4 ± 5.7 (range, 3.5-25.4), 10.4 ± 5.5 (range, 3.7-26.4), 6 ± 4.1 (range, 1.3-20.6), and 6.5 ± 4.2 (range, 1.8-19.7), respectively. The uptake in the tubarial glands was comparable with that of the tumor but less compared with other major salivary glands. Ours is the first study demonstrating the quantitative uptake of tubarial salivary glands in detail. Because the tubarial glands uptake and the anatomical location are similar to that of the tumor, these physiological uptakes must be borne in mind to circumvent false-positive interpretations and care must be given during the planning of stereotactic radiotherapy for JNAs.