Robinson, S I

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.

Abstract Introduction Solid tumors modify local angiogenesis and co-opt surrounding vasculature to maintain energy supply required for ongoing growth. This process is often complicated by metastasis and hemorrhage. Pulmonary tumors can rarely create intrapulmonary shunt physiology and hypoxemia in this manner; this has been described most often in bronchoalveolar carcinoma. We present a case of malignant intrapulmonary shunt occurring with spindle cell sarcoma, which resolved with arterial embolization. Case Presentation A 72-year-old male with a history of stage IV spindle cell sarcoma with abdominal, vertebral, and pulmonary metastases presented to an outpatient appointment with three weeks of fatigue and decreased exercise tolerance. He had no history of parenchymal lung disease nor any home oxygen requirement. In clinic, he was found to require 6L per minute of supplemental oxygen to maintain saturation of 88%. He was directly admitted to the oncology service. Initial laboratory evaluation was unremarkable. CT imaging demonstrated normal lung parenchyma, no pulmonary embolism, and an 11cm vascular tumor involving proximal branches of the local pulmonary artery (Figure). Transthoracic echocardiography (TTE) with agitated saline revealed a large intrapulmonary shunt. As the patient had limited response to oxygen therapy, this intra-tumoral shunt was deemed the most likely cause of his hypoxemia. Surgical resection was considered but was deemed to confer limited clinical benefit in the setting of multiple metastases. Embolization of the local pulmonary artery was therefore pursued with Interventional Radiology. The patient tolerated the procedure well with complete resolution of hypoxemia post-procedure. His energy and mobility improved, and he was discharged home. Three months later, he continued to require no supplemental oxygen. Discussion While shunt physiology is commonly part of the differential for hypoxemia, it is rarely described as an oncologic complication. This appears to be the first report of such pathology in a sarcoma patient, and the first to report shunt resolution through arterial embolization rather than surgical resection or systemic anti-tumor therapy. In addition, previous cases typically describe shunt detection via selective pulmonary arterial occlusion by Swan-Ganz catheter, whereas here the noninvasive TTE with agitated saline was sufficient. While the few existing reports highlight good response to lobectomy or pneumonectomy, this case highlights the potential for minimally invasive vascular intervention. Despite the metastatic nature of this patient’s disease, he received significant, rapid physiologic and functional benefit from a procedure with less morbidity. Maintaining suspicion of intra-tumoral shunt physiology is appropriate for patients with vascular pulmonary masses and hypoxemia. This abstract is funded by: None