Ho, Thanh

Abstract Background: Solitary fibrous tumors (SFT) make up less than 5% of sarcomas. The Demicco model stratifies risk of metastasis based on age, tumor size, mitotic count, and necrosis. Patients (pts) with relapsed disease have limited options. We evaluated outcomes of systemic therapies (tx) to treat SFT. Methods: A retrospective analysis was performed of pts with intermediate-to-high risk SFT confirmed by soft tissue pathologists at a multi-site health system from 1999 – 2024. Demographics, tx, and pt outcomes were analyzed. Radiographic response was abstracted from documentation by treating provider. Results: Sixty pts had intermediate-to-high risk SFT, of which 21 pts received systemic tx. Of these, 12 were male, median age at diagnosis 62.8 years (41.0 – 82.7 yrs). Tumors originated from chest (11, 52.4%), abdomen (5, 23.8%), pelvis (4, 19.0%), and skull (1, 4.8%). All pts had surgery for primary tumor, median size 16.0 cm (7.8 – 43.0), and 14 (66.7%) had surgery at relapse. Eight pts (38.1%) had perioperative radiation therapy (RT); 12 (57.1%) had palliative RT. Five (23.8%) had ablation. Of the 21 pts, 2 (9.5%) had perioperative chemotherapy (chemo). Twenty pts (95.2%) received median 2 lines (1 – 6) of palliative systemic tx (1 pt did not pursue any). One pt had partial response on dacarbazine, otherwise best clinical response was stable disease (SD, 53.1% vascular endothelial growth factor inhibitors (VEGFi), 40% chemo) or disease progression (PD). Most pts received VEGFi: 11 pts had sunitinib (median 3.1 months, range 1.0 – 10.6 mo), 11 pts had pazopanib (4.1 mo, 0.1 – 38.7), and 10 pts had temozolomide/bevacizumab (5.6 mo, 1.0 – 15.8). VEGFi was dose reduced or held in 59.4% . Discontinuation due to toxicity occurred in 34.4% of pts treated with VEGFi vs 26.7% of pts treated with chemo. Five pts received liposomal doxorubicin (median 4.8 mo, range 3.5 – 11.3). Four pts had doxorubicin with dacarbazine, ifosfamide or olaratumab (2.8 mo, 0.7 – 8.5). Two pts received dacarbazine (1.9 and 9.6 mo, respectively), and 2 pts received gemcitabine/docetaxel (0.9 and 4 mo). Eribulin and trabectedin (1 pt, respectively) were used for less than 1 mo. Tx was held or dose reduced for 1 pt on doxorubicin/dacarbazine and 1 pt on gemcitabine/docetaxel. Three pts had immunotherapy (IO, 2 pts pembrolizumab, 1 pt nivolumab/ipilimumab) and stopped for PD (2 pts) or toxicity (1 pt) after 2 mo or less. Two pts participated in clinical trials. Median time from primary surgery to relapse was 2.0 yrs (0.0 – 12.3). Sixteen pts died (76.2%), 14 from SFT. Median time from relapse to death or last contact was 4.1 yrs (0.5 – 14.7). Median overall survival from diagnosis to death/last contact was 6.6 yrs (0.6 – 27.0). Conclusion: Perioperative chemo was rarely used to treat intermediate-to-high risk SFT. For relapse, VEGFi use was more common than chemo, with more pts achieving SD and receiving longer duration of tx. VEGFi had greater toxicity and subsequent discontinuation. No benefit was observed in few pts who received IO. Clinical trial participation was uncommon. Citation Format: Miranda Lin, Brittany Siontis, Steven Robinson, Scott Okuno, Thanh Ho. Systemic Therapy and Outcomes in Patients with Intermediate or High-Risk Solitary Fibrous Tumor [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Breaking Barriers in the Fight against Rare Cancers; 2026 Jul 18-20; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(14_Suppl):Abstract nr B054.