ESTRO 2023 - Abstract Book

S1278

Digital Posters

ESTRO 2023

Conclusion SBRT is a considerable option for oligometastatic patients due to its excellent local and biochemical control with a negligible toxicity profile. The rate of distant progression means that the role of SBRT must be reassessed with the aim of delaying systemic therapy or as part of a combination treatment.

PO-1574 Spine stereotactic radiosurgery in the management of metastatic pheochromocytoma

T. Beckham 1 , B. Amini 2 , T. Briere 3 , M. Wang 4 , D. Yeboa 5 , M.F. McAleer 5 , M. Tom 4 , S. Perni 4 , L. Rhines 6 , C. Tatsui 6 , R. North 6 , C. Alvarez-Breckenridge 6 , A. Ghia 4 , J. Li 4 1 MD Anderson Cancer Center, Radiation Oncology, Houston , USA; 2 MD Anderson Cancer Center , Diagnostic Imaging , Houston , USA; 3 MD Anderson Cancer Center, Radiation Physics, Houston, USA; 4 MD Anderson Cancer Center, Radiation Oncology, Houston, USA; 5 MD Anderson Cancer Center, Radiation Oncology , Houston, USA; 6 MD Anderson Cancer Center, Neurosurgery, Houston, USA Purpose or Objective Despite aggressive primary treatment, up to 13.5% of patients diagnosed with pheochromocytoma may develop metastases, most often affecting the axial skeleton. Given that systemic therapy options are often inadequate, local therapy remains important for management of these patients. Historically poor responses to standard fractionated radiotherapy have led to the consideration of stereotactic radiosurgery as an option to overcome potential radioresistance and provide durable local control of these tumors. Here we report an update of our institutional experience in treating spine metastases from pheochromocytoma with spine stereotactic radiosurgery (SSRS). Materials and Methods We retrospectively reviewed our institutional SSRS database for patients with metastatic pheochromocytoma treated with SSRS from 2000-2022. We identified 9 patients treated to 41 SSRS targets. Local control (LC) and subsequent development of pathological compression fracture was evaluated using magnetic resonance imaging (MRI) and/or positron emission tomography (PET). Overall survival (OS) and actuarial LC were estimated using the Kaplan-Meier method. Results Our experience includes 41 SSRS targets encompassing 64 vertebral levels in 9 patients. Targeted vertebral levels included cervical (12.5%), thoracic (50.0%), lumbar (23.4%) and sacrum (14.0%). Epidural disease was present in 29.3% of targets, and 12.2% of targets were treated postoperatively. The most common SSRS prescriptions were 27Gy in 3 fractions (58.6%) and 24Gy in 1 fraction (41.5%). Median follow-up for treated lesions was 23 months (range 1.1-86.2 months). Local failure was observed in 2 SSRS targets in the same patient – a thoracic lesion 15.0 months after 24Gy in 1 fraction and another thoracic target 9.4 months after 27Gy in 3 fractions. This results in a crude local failure rate of 4.9% of SSRS targets. Actuarial LC at 1, 2, and 4 years were 96.9%, 92.3%, and 92.3%, respectively. Three pathologic compression fractures developed after SSRS between 8.4 and 15 months after treatment, none requiring invasive intervention. Kaplan Meier OS rates at 1- and 2-years following patient’s initial SSRS treatment were both 66.7% with a 4-year OS of 50.0%. Conclusion Metastatic pheochromocytoma is rare with limited therapeutic options. Radiation therapy plays an important role in palliation and disease management, however there are very few reports on the efficacy of radiation modalities against this disease. We report an update on our institutional experience with SSRS in these patients. SSRS is effective in these patients with local failure a rare occurrence. In appropriately selected patients with spine metastases from pheochromocytoma, SSRS is a reasonable option for local control and symptom palliation.