Clinical Outcomes and Quality of Life After Proton Therapy for Cranial and Extracranial Solitary Fibrous Tumors

Abstract Objectives Solitary fibrous tumors (SFTs) are rare malignancies. Surgical resection, particularly gross total resection, is the mainstay of therapy. The benefit of postoperative radiotherapy remains uncertain, with inconsistent findings across studies. Existing literature predominantly reported photon-based radiotherapy. This study evaluates clinical outcomes, late toxicities, and quality of life (QoL) in patients with SFTs treated with postoperative pencil beam scanning proton therapy (PT). Methods We performed a retrospective single-center analysis of patients with histologically confirmed cranial or extracranial SFTs treated with PT. Local control (LC) was assessed using BT-RADS or RECIST criteria. Toxicities were recorded using CTCAE v5.0, and QoL was assessed prospectively in patients with cranial SFTs. Kaplan-Meier analysis was used to estimate overall survival (OS) and LC, with subgroup comparisons made using the log-rank test. Results Seventeen patients were included, with a majority presenting with cranial SFTs (64.7%). After a median follow-up of 47 months (range 7—208 months), OS was 100%. The 5-year LC rate was 81.8% (95% CI: 61.9—100%) for the entire cohort. Acute toxicities were limited to grade 1–2. Two patients (11.8%) experienced severe late toxicity. Overall QoL appeared broadly stable over time and was comparable to reference population values. Conclusion PT provided encouraging preliminary OS and LC rates in patients with cranial and extracranial SFTs. Despite a low rate, the severity of these late toxicities highlights substantial risks near the CNS axis. Advances in knowledge This retrospective single-center study provides the largest analyzed cohort of patients with cranial and extracranial SFTs treated with proton therapy to our knowledge.