Toward Radioguided Surgery with β- Decays: Uptake of a Somatostatin Analogue, DOTATOC, in Meningioma and High-Grade Glioma

A novel radioguided surgery (RGS) technique for cerebral tumors using beta(-)radiation is being developed. Checking for a radiotracer that can deliver a beta(-)emitter to the tumor is a fundamental step in the deployment of such a technique. This paper reports a study of the uptake of Y-90-DOTATOC in meningiomas and high-grade gliomas (HGGs) and a feasibility study of the RGS technique in these types of tumor. Estimates were performed assuming the use of a beta(-)probe under development with a sensitive area 2.55 mm in radius to detect 0.1-mL residuals. Methods: Uptake and background from healthy tissues were estimated on Ga-68-DOTATOC PET scans of 11 meningioma patients and 12 HGG patients. A dedicated statistical analysis of the DICOM images was developed and validated. The feasibility study was performed using full simulation of emission and detection of the radiation, accounting for the measured uptake and background rate. Results: All meningioma patients but one with an atypical extracranial tumor showed high uptake of DOTATOC. In terms of feasibility of the RGS technique, we estimated that by administering a 3 MBq/kg activity of radiotracer, the time needed to detect a 0.1-mL remnant with 5% false-negative and 1% falsepositive rates is less than 1 s. Actually, to achieve a detection time of 1 s the required activities to administer were as low as 0.2-0.5 MBq/kg in many patients. In HGGs, the uptake was lower than in meningiomas, but the tumor-to-nontumor ratio was higher than 4, which implies that the tracer can still be effective for RGS. It was estimated that by administering 3 mBq/kg of radiotracer, the time needed to detect a 0.1-mL remnant is less than 6 s, with the exception of the only oligodendroma in the sample. Conclusion: Uptake of Y-90-DOTATOC in meningiomas was high in all studied patients. Uptake in HGGs was significantly worse than in meningiomas but was still acceptable for RGS, particularly if further research and development are done to improve the performance of the beta(-)probe.