NIMG-66. USING 68GA-DOTATATE PET FOR POSTOPERATIVE GAMMA KNIFE RADIOSURGERY PLANNING IN PATIENTS WITH MENINGIOMA

Abstract

Abstract BACKGROUND Patients with meningiomas are typically treated with maximal safe surgical resection. After subtotal resection or at the time of tumor recurrence, stereotactic radiosurgery (SRS) is often used as the treatment of choice. While magnetic resonance imaging (MRI) is typically used for SRS target delineation, differentiating tumor growth from postoperative change can be challenging. 68Ga-DOTATATE, a positron emission tomography (PET) radiotracer targeting the somatostatin receptor type 2 (SSTR2), has been shown to be a reliable biomarker of meningiomas. METHODS We present a consecutive case series of 13 patients with pathology-proven meningioma who received a 68Ga-DOTATATE PET prior to SRS between April 2019 and April 2021. Treatment planning was done at first using MRI only. The DOTATATE-PET images were then used to assess the accurate identification of tumor. RESULTS Ten of the patients had WHO grade 2 meningioma and three patients had WHO grade 1 tumor. Nine patients had recurrent meningiomas and four patients had newly diagnosed disease. Overall, the 68Ga-DOTATATE PET scan revealed additional tumor beyond what was seen on MRI in 5/13 patients. The SRS plan was changed to intensity-modulated radiation therapy (IMRT) for three patients and to octreotide injection in one patient. In one patient, after 68Ga-DOTATATE PET identified previously unrecognized recurrent meningioma in the resection cavity, SRS was performed. In three others, questionable tumor recurrence was seen on MRI, and then confirmed on 68Ga-DOTATATE-PET, but patient observation only was continued due to the small lesion size. CONCLUSION Incorporation of 68Ga-DOTATATE PET data changed SRS treatment in 5/13 our patients with meningioma after prior surgery. We have made this a routine part of our treatment planning and we recommend this method to optimize the use of SRS or RT in these patients. Further data collection is ongoing.