Utilization of Gallium-68 Dotatate PET CT for the Evaluation of Head and Neck Paraganliomas in a Major Tertiary Academic University Neurosurgical Center

Introduction: Head and Neck Paragangliomas (HNPGLs) are rare neuroendocrine tumors. They are somatostatin receptor (SSTR) positive which the SSTR is expressed on the cell surface of neuroendocrine cells. They are routinely treated with surgery, however subtotal resection of the tumor is quite common. Postoperative radiation therapy remains an additional treatment option in many cases. The gold standard for postoperative assessment is contrast-enhanced magnetic resonance imaging (MRI), however MRI is limited in its capability to distinguish residual tumor from postoperative changes. Gallium-68 (Ga-68) Dotatate can be a reliable imaging biomarker of HNPGLs because of its specific targeting of the SSTR which is highly expressed in HNPGLs.

Methods: A total 25 patients with preoperative clinical suspicion of PGLs or postoperative pathology proven HNPGLs underwent a Ga-68 Dotatate PET CT evaluation between January 2023 and January 2024. Patients received an intravenous administration of 5 mCi Ga-68 Dotatate followed by a 60 minute uptake period in a dark quiet room. PET CT images of the brain where fused to contrast enhanced MRI. The MRI was a 3T scanner and protocol was with and without to contrast enhanced MRI per protocol. All studies were reviewed by a specialized Nuclear Medicine physician experienced in Ga-68 Dotatate PET CT interpretation.

Results: Of a total of 25 patients who underwent a Ga-68 dotatate PET/MRI for evaluation of HNPGLs, 5 of these were at initial diagnosis for delineation of tumor extent and 20 were post resection for determination of residual/recurrent tumor involvement. Of the 20 patients evaluated postoperatively, 9 demonstrated unifocal tumor residual/recurrent tumor involvement and 10 demonstrated multifocal residual/recurrent tumor involvement.

Conclusions: Ga-68 Dotatate PET CT is a novel imaging technique which allows for improved diagnostic evaluation of HNPGLs by combining a receptor specific targeted molecular imaging biomarker with optimal anatomic characterization. Ga-68 Dotatate PET CT allows for better detection of lesions in patients with HNPGLs and better delineates the extent of gross tumor involvement than does contrast-enhanced MRI alone. Equally important, Ga-68 Dotatate PET CT better discriminates between recurrent/residual tumor and scar tissue after prior surgery, with higher sensitivity and specificity compared with MRI alone. This information is of potentially great value for patients with HNPGLs and can play an important role for improving preoperative and postoperative treatment planning strategy.

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