A retrospective multicenter study on solitary fibrous tumors: investigation of clinical features and management approaches

Aims: Solitary fibrous tumors are exceedingly rare neoplasms, for which surgical resection remains the cornerstone of treatment; however, long-term surveillance is imperative due to the significant risk of recurrence. We aimed to evaluate tumor characteristics and treatment responses in this multicenter study. Methods: Sixty-eight adult patients with histologically confirmed solitary fibrous tumor (SFT) diagnosed between 2010 and 2024 from seven cancer centers in Turkiye were included. Clinical and pathological features along with treatment outcomes were assessed. Results: The majority of patients (65/68 pts, 95%) presented with localized disease and underwent primary resection, while 3 patients had metastatic disease at the time of diagnosis. Further analyses were performed only in patients with localized disease. Median follow-up time was 41.7 months. All patients underwent primary surgery; R0 resection was achieved in most patients (66.2%). Five -year DFS and OS were 67% and 87%, respectively. DFS of extrameningeal SFTs was further evaluated according to clinicopathological variables. Low Ki-67 Labeling Index, low mitotic rate, and younger age were found to be associated with longer DFS. Response rates to first-line systemic therapy after recurrence was 27% with chemotherapy and while no objective responses were achieved with pazopanib. Two patients experienced disease control for up to 11 months with pazopanib. This study is limited by the relatively small sample size and the heterogeneity arising from the inclusion of both meningeal and extrameningeal tumors located at different anatomical sites. Conclusion: Localized SFTs usually have favorable prognosis. Patients with extrameningeal SFTs with younger age, low Ki-67 Index and low mitotic rate have longer survival. Once relapsed, repeat surgical resection should be pursued when possible. Response rates to systemic treatment is generally low.