Current status of SSR-directed imaging and therapy in meningioma

Abstract

Meningiomas are the most common tumours of the central nervous system in adults. In clinical routine, their diagnostic workup prior to subsequent therapies such as resection and radiotherapy usually consists of contrast-enhanced MRI and CT of the brain. However, there are several diagnostic uncertainties in the clinical workup, which standard morphological imaging fails to resolve. Molecular imaging has an emerging role for the diagnosis of meningiomas, which characteristically show high expression of the somatostatin receptor subtype 2 (SSR). PET imaging with selective ligands can visualize and quantify this expression against low background signal in healthy brain. Moreover, SSR-directed radioligands labeled with beta-emitters can be effective for radiopeptide therapy (RPT) in patients with recurrent or refractory meningioma. A literature search on the PubMed literature database was conducted using the terms “meningioma”, “PET”, “somatostatin receptor”, “SS(T)R”, “DOTATATE”, “DOTATOC”, “Radiopeptide therapy”, “imaging”, “therapy” alone and in combination, extending until February 2019. The search results were augmented by the authors’ own literature files. We summarize the current state of SSR-directed imaging in patients with meningioma regarding the distinct clinical applications for initial diagnosis, differential diagnosis, surgery and radiotherapy planning. Our review also summarizes SSR imaging for the differentiation of recurrent meningioma tissue from post-therapeutic changes within the individual follow-up. Moreover, we discuss the clinical value and place of SSR-directed RPT in patients with refractory or recurrent meningioma. Molecular imaging with SSR-directed radioligands contributes to the diagnostic work-up of meningioma patients by providing information that is absent from structural MR or CT imaging. Targeted SSR RPT offers well-tolerated treatment options in patients with refractory or recurrent meningioma.