Imaging assessment of tumor densities and sizes following pazopanib treatment for central nervous system solitary fibrous tumors with multiple extracranial metastases: A case series

Central nervous system (CNS) solitary fibrous tumors (SFTs) are rare but aggressive, often metastasizing to extracranial regions, with no established treatments apart from surgery. Pazopanib, a multikinase angiogenesis inhibitor, is used to treat extracranial SFTs; however, its efficacy for treating CNS SFTs remains unclear. To address this issue, the efficacy of pazopanib was investigated, focusing on tumor density and size in CNS SFTs with extracranial metastases after initiation, interruption or resumption of pazopanib treatment. The present study retrospectively reviewed 3 consecutive cases of CNS SFTs showing extracranial metastases that were referred to Kochi Health Sciences Center (Kochi, Japan) between January 2018 and April 2024 and were treated with pazopanib. All measurable lesions observed via contrast-enhanced computed tomography (CT; 50 lesions) and magnetic resonance imaging (MRI; 21 lesions) were evaluated. Cases 2 and 3, meeting the Choi criteria, showed stable disease and achieved partial response after pazopanib initiation, respectively. In Case 1, both intracranial and extracranial tumor CT densities decreased after initiation and resumption of pazopanib treatment. However, both tumor CT sizes increased after interruption of pazopanib treatment. In Case 2, MRI revealed decreases and increases in the intracranial tumor size after initiation and interruption, respectively. Notably, pazopanib interruption caused rapid infratentorial tumor growth and death. Case 3 showed decreased extracranial tumor CT densities and sizes after pazopanib initiation, with pazopanib administered for 3.5 years. Thus, pazopanib may offer the potential to control both intracranial and extracranial tumors in patients with CNS SFTs with extracranial metastasis; however, treatment interruption requires careful consideration.