RADT-83. OUTCOMES OF SOLITARY FIBROUS TUMOURS OF CNS (SOFT)

Abstract BACKGROUND Solitary fibrous tumours (SFT) of the central nervous system (CNS), formerly known as hemangiopericytomas (HPC), are rare mesenchymal neoplasms characterized by NAB2-STAT6 gene fusions and STAT6 nuclear expression. The 2021 WHO classification describes a spectrum of three histological grades, with increasing grade correlating with poorer prognosis. Standard treatment includes maximal safe surgical resection, with adjuvant radiotherapy (RT) often added in cases of subtotal resection or high-grade disease. However, data regarding long-term outcomes and the benefit of RT remain limited. MATERIAL AND METHODS We retrospectively reviewed patients with CNS SFT treated at our institution between 2003 and 2020. Clinical features, treatment details, and outcomes were extracted from institutional records. Overall survival (OS) and progression-free survival (PFS) were analyzed using Kaplan–Meier methods, and associations between clinicopathological factors and outcomes were assessed using log-rank tests and Cox regression. Subgroup analysis stratified patients into three risk groups: low risk (Grade 1, any extent of resection, or Grade 2 with gross total resection), intermediate risk (Grade 2 with biopsy or subtotal resection), and high risk (Grade 3, any extent of resection), as per prior literature. RESULTS Eighty-two patients were included (median age: 41 years; 66% male). The majority were intracranial (97.5%, predominantly supratentorial), and 93% were Grade II or III. Gross or near-total resection was achieved in 83% of cases, and 75% received postoperative RT (PORT). At a median follow-up of 48 months, the 5-year OS and PFS were 89% and 54%, respectively. Tumour grade and extent of resection were not significantly associated with survival. Among 52 patients receiving PORT, subgroup analysis revealed no significant outcome differences between intermediate- and high-risk groups. CONCLUSION Patients with CNS SFT/HPC treated with surgery and adjuvant therapy achieved favourable long-term outcomes in our series. PORT improves high-risk patient outcomes to levels comparable to intermediate-risk patients. Further prospective studies are warranted.