68Ga-DOTATOC-PET/MRI—A Secure One-Stop Shop Imaging Tool for Robotic Radiosurgery Treatment Planning in Patients with Optic Nerve Sheath Meningioma

Abstract

Optic nerve sheath meningiomas (ONSM) are rare but can lead to irreversible blindness. Hybrid imaging may enhance tumor delineation and diagnostic accuracy via receptor binding. However, relevant clinical data for ONSM are lacking. We evaluated the feasibility of receptor-based hybrid imaging prior to robotic radiosurgery (RRS). We retrospectively analyzed all of our institution’s patients with suspected ONSM who underwent combined positron emission tomography and magnetic resonance imaging (PET/MRI) with gallium-68-labeled (DOTA0-Phe1-Tyr3) octreotide (Ga68-DOTATOC) before RRS between 2018 and 2019. Eight patients with ten suspected ONSM (female = 7; median age, 51.2 years; IQR, 43.0–66.0) were included. Nine out of ten ONSM were deemed PET-positive with a median standard uptake value (SUV) max of 5.6 (IQR, 2.6–7.8). For all nine ONSM that presented 68Ga-DOTATOC uptake, hybrid PET/MRI was used for target volume contouring prior to RSS. At a median follow-up of 11.7 months (IQR, 9.4–16.4), tumor control was achieved in all patients. Radiosurgery resulted in the improvement of visual acuity in two of eight patients, whereas six showed stable vision. Ga68-DOTATOC-PET/MRI can be used for target volume contouring prior to RRS for ONSM as it enables safe treatment planning and improves diagnostic accuracy.

The Role of [68Ga]Ga-DOTA-SSTR PET Radiotracers in Brain Tumors: A Systematic Review of the Literature and Ongoing Clinical Trials

“…The initial search yielded 1606 published articles (PubMed: 803; Scopus: 673; Web of Science: 107; Cochrane: 23). A total of 63 studies were included with the a priori criteria: 25 were case reports and 38 were case series, categorized with levels of evidence IV and V, respectively [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ,…”

“…DOTATOC (78.2%) was utilized more frequently than DOTATATE (21.8%), and Pelak et al [ 69 ] also reported the use of DOTANOC in 19 patients. [ 68 Ga]Ga-DOTA-SSTR PET studies were mostly fused with CT/MRI studies and implemented to improve volume contouring for radiation planning, such as stereotactic radiotherapy (SRT) [ 20 , 26 , 28 , 33 ], intensity-modulated radiotherapy (IMRT) [ 27 , 29 ], conventional radiotherapy [ 46 , 49 , 51 , 66 ], cyber knife radiosurgery (CKRS) [ 17 , 18 ], and carbon/proton therapy [ 32 , 69 ]. The implementation of [ 68 Ga]Ga-DOTA-SSTR PET proved to significantly improve target definition in meningiomas of the skull base, parafalcine, intraosseous, or affecting the optic nerve sheath, also favoring reduced radiation doses to adjacent organs at risk.…”

“…Comparable results were also obtained in other studies, which further reported [ 68 Ga]Ga-DOTA-SSTR PET detection of additional information on meningiomas not detected at MRI [ 28 , 69 ] and superior target delineation of post-surgery/radiation meningioma recurrence from post-treatment tissue scarring or edema/pseudoprogression [ 27 , 29 ]. The role of [ 68 Ga]Ga-DOTA-SSTR PET for tumor volume contouring has been validated for FSRT [ 20 , 66 ], radiosurgery [ 17 , 18 ], and proton/carbon therapy [ 32 , 69 ] planning, optimizing PTV delineation, improving target dose escalation, and minimizing radiation to organs at risk, especially for the highly challenging optic nerve sheath meningiomas [ 18 ]. Likewise, d’Amico et al [ 36 ] confirmed the potential benefits of using [ 68 Ga]Ga-DOTA-SSTR PET for radiosurgery planning in pituitary carcinomas infiltrating the cavernous sinus, as it allows precise tumor contouring of residual post-surgery volumes.…”

“…PET/CT and, more recently, hybrid PET/MRI systems, show a superior diagnostic accuracy compared to CT and MRI protocols, allowing a better detection and volume definition of skull base and transosseous meningiomas, and also post-surgery residual tumors [ 13 , 14 , 15 , 16 ]. With these premises, [ 68 Ga]Ga-DOTA-SSTR PET scans are frequently implemented as imaging adjuncts to guide surgical resection and radiation treatment planning of complex meningiomas, improving safe and effective target delineation [ 17 , 18 , 19 , 20 ]. [ 68 Ga]Ga-DOTA-SSTR PET scans may also be used to study the pretherapeutic tumor uptake of DOTA-chelator tracers and predict tumor response to targeted DOTA-labeled β-emitting radionuclides (i.e., neurotheranostics), as described for radiation-resistant meningiomas [ 21 ].…”

PET Imaging in Neuro-Oncology: An Update and Overview of a Rapidly Growing Area

“…PET with SSTR ligands is particularly useful in cases of ambiguous, non-contributive MRI and for specific regions which are known to be difficult to appreciate by MRI, such as the base of the skull and bony structures. The rare but aggressive optic nerve sheath meningioma entity almost invariably takes up SSTR ligands [ 59 ]. PET with SSTR ligands is thus better suited than contrast-enhanced MRI to delineate tumor margins, which is potentially informative for tumor resection.…”