Radio Guided Surgery with Intra-operative Use of a [cu64]dotatate-directed Gamma Probe

Introduction: Meningiomas are the most common primary intracranial neoplasms. Gross total resection (GTR) is not achieved in up to 50% of patients, with resulting decrease in progression-free and overall survival (PFS/OS). Intraoperative assessment of resection extent using the Simpson Grade (SG) was traditionally employed to predict recurrence but has recently been shown less accurate that post-operative MRI scans. Techniques that improve intraoperative assessment of resection extent are thus a paramount goal in meningioma management. Radio-guided surgery, is widely used in sentinel node mapping e.g. in breast surgical oncology, however has not been previously applied in brain tumor surgery.

Somatostatin receptor (SSTR)-targeted PET has improved meningioma diagnosis and management. [Cu64]DOTATATE is a clinically approved PET radiotracer avidly binding SSTR2 with properties similar to [Ga68]DOTATATE, however with a significantly longer half-life of 13 hours. We aimed to demonstrate feasibility of immediate preoperative [Cu64]DOTATATE PET/MRI and subsequent intraoperative tumor detection using a handheld gamma probe device.

Methods: One patient with a left temporal meningioma was enrolled on our prospective IRB-approved feasibility study. Following intravenous administration of 4 millicuries of [Cu64]DOTATATE, patient underwent dedicated dynamic brain PET/MRI approximately 7 hours prior to surgical resection. Intraoperative gamma probe readings were taken epidurally before resection, on the brain surface at tumor and control points, during resection, and immediately after resection.

Results: Gamma probe readings were 10x higher than background after exposing the tumor, and decreased by 50% after debulking, thus providing proof of feasibility of intraoperative gamma probe guidance in meningioma resection using [Cu64]DOTATATE.

Conclusion : Our pilot study for the first time demonstrates feasibility of preoperative PET with in vivo radioguided surgery in meningioma, demonstrating variation in gamma probe readings in correlation with location and presence of tumor, thus laying the foundation for larger-scale prospective trials which may improve meningioma resection extent and thereby clinical outcomes.