Meningioma theranostics: a retrospective analysis of somatostatin receptor PET/CT imaging and peptide receptor radionuclide therapy.

Abstract

This study aims to evaluate differences in PET/CT imaging of meningioma using both gallium-68- and fluorine-18-labelled somatostatin receptor (SSTR) tracers, to characterize incidentally detected meningiomas on SSTR PET/CT, and to analyse institutional experience with Peptide Receptor Radionuclide Therapy (PRRT) in meningioma. This single centre retrospective study included all SSTR PET/CT scans of meningioma patients (2007-2024) performed with [⁶⁸Ga]Ga-DOTATOC, [⁶⁸Ga]Ga-DOTATATE or [¹⁸F]AlF-NOTA-octreotide. For lesions ≥ 1cm³, tumour uptake was quantified using three distinct delineation methods: an absolute SUV threshold of 2.3, a relative threshold of 1.73 × SUV_peak of a meningeal reference region, and a relative threshold of 11% of the lesion's SUV_max. Tumour-to-background ratios were calculated. Meningioma patients treated with PRRT were identified from our institutional registry (2016-2024). Of 4,136 SSTR PET/CTs, 152 patients with 171 SSTR-expressing meningiomas were included. Incidental meningiomas were found in 3.7% of patients imaged for unrelated indications. Quantitative analysis of 86 lesions (≥ 1 cm³) showed robust uptake for [¹⁸F]AlF-NOTA-octreotide (n = 7), [⁶⁸Ga]Ga-DOTATATE (n = 73), and [⁶⁸Ga]Ga-DOTATOC (n = 6), without significant between-tracer differences across delineation strategies. All tracers demonstrated high tumour-to-meningeal uptake ratios with ratios ranging from 51 to 146 for [¹⁸F]AlF-NOTA-octreotide, 10-329 for [⁶⁸Ga]Ga-DOTATATE, and 12-76 for [⁶⁸Ga]Ga-DOTATOC, confirming excellent tumour-to-background contrast. Among 12 heavily pretreated patients receiving PRRT, disease control rate was 50%, median progression-free survival 8 months, and overall survival 20 months. SSTR PET/CT enables high-contrast meningioma visualisation. [¹⁸F]AlF-NOTA-octreotide seems clinically interchangeable with gallium-68-labelled tracers, while offering logistical advantages. PRRT achieves meaningful disease stabilisation, supporting further validation in prospective randomised studies.