Utilization of Gallium-68 Dotatate PET MRI for the Evaluation of Meningioma in a Major Tertiary Academic University Neurosurgical Center

Objectives: One of the most common primary intracranial tumors are meningiomas. They are customarily treated with surgery, however subtotal resection of the tumor is 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 meningioma because of its specific targeting of the somatostatin receptor 2A (SSTR2A) which is highly expressed in meningiomas. Ga-68 dotatate PET/MRI combines complimentary targeted molecular imaging with anatomic detail to achieve optimal evaluation.

Methods: A total 27 patients with preoperative clinical suspicion of meningioma or postoperative pathology proven meningioma underwent a Ga-68 dotatate PET/MRI evaluation between January 2020 and January 2021 at University Hospitals of Cleveland Medical Center. Patients received an intravenous administration of 5 mCi Ga-68 dotatate followed by a 60 minute uptake period in a dark quiet room. PET images of the brain were then acquired along with a contemporaneous contrast enhanced MRI on a combined PET/MRI scanner. MRI sequences included Axial T2, FLAIR, DWI, gradient echo T2, and pre/post gadolinium contrast T1 weighted images. All studies were reviewed by a specialized Nuclear Medicine physician experienced in Ga-68 dotatate PET/MRI interpretation.

Results: Of a total of 27 patients who underwent a Ga-68 dotatate PET/MRI for evaluation of meningioma, 3 of these were at initial diagnosis for delineation of tumor extent and 24 were post resection for determination of residual/recurrent tumor involvement. Of the 24 patients evaluated postoperatively, 11 demonstrated unifocal tumor residual/recurrenct tumor involvement and 13 demonstrated multifocal residual/recurrent tumor involvement.

Conclusions: Ga-68 dotatate PET/MRI is a novel imaging technique which allows for improved diagnostic evaluation of meningioma by combining a receptor specific targeted molecular imaging biomarker with optimal anatomic characterization. Ga-68 dotatate PET/MRI allows for better detection of lesions in patients with meningioma and better delineates the extent of gross tumor involvement than does contrast-enhanced MRI alone. Equally important, Ga-68 dotatate PET/MRI 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 meningioma and can play an important role for improving preoperative and postoperative treatment planning strategy.