2305 - Treatment Outcomes and Toxicities of Stereotactic Body Radiation Therapy for Sarcomas Involving Weight-Bearing Bones - A Single Institution Study
Presenter(s)
J. C. Bastick III1, J. Kocsis2, P. Baucco2, C. A. Reddy1, E. Somasundaram3, J. G. Scott1, L. Angelov4, P. Anderson5, S. Zahler5, M. Trucco5, S. Thomas5, P. Qi1, A. Magnelli1, S. R. Campbell1, and E. S. Murphy1; 1Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic Foundation, Cleveland, OH, 2Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, 3Massachusetts General Hospital, Boston, MA, 4Department of Neurological Surgery, Cleveland Clinic Foundation, Cleveland, OH, 5Department of Pediatric Hematology Oncology and Blood and Marrow Transplantation, Cleveland Clinic Foundation, Cleveland, OH
Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has emerged as an effective treatment for metastatic sarcomas involving weight-bearing bones. Studies demonstrate excellent local control rates of 76-95% at 1 year; however, treatment of weight-bearing bones presents unique challenges. Pathologic fracture rates range from 3-10% following SBRT to non-spine bone metastases, with larger planning target volumes and lytic lesions conferring increased risk. Vertebral compression fracture is another well-recognized complication of spine SBRT, with rates of approximately 14%. Higher biologically effective doses appear to improve local control, though optimal dose-fractionation schemes remain incompletely defined. This study reports institutional experience with SBRT for sarcoma recurrence and metastases in weight-bearing bones to inform dose-fractionation strategies and toxicity risk.
Materials/Methods: This retrospective cohort study includes all patients at our institution treated with SBRT between 2017-2024 for recurrent or metastatic sarcomas involving weight-bearing bones, excluding mobile spine. Data extracted includes patient demographics, tumor characteristics (histology, location, size), SBRT parameters (dose, fractionation, BED), and concurrent systemic treatments. Outcomes evaluated include local control, overall survival, and rates of grade 3+ toxicity per CTCAE v5.0 with a particular emphasis on fracture rate.
Results: From 2017-2024, 39 patients fit inclusion criteria for this study, with a total of 60 lesions treated involving weight bearing bones. The median clinical follow up was 12.4 months and median OS was 16.2 months. The median age at the time of treatment was 22 years (range 6-69) and median KPS was 90 (range 70-100). Treated lesions include axial skeleton (3.4%), sacrum (18.3%), upper extremity (15.0%), and lower extremity (63.3%). A variety of dose fractionation schemes were used, with a median BED3 of 130 Gy. Predominant SBRT doses were regimens of 40 Gy in 5 fractions (43.3%) and 21 Gy in 3 fractions (21.7%). The local control rate by lesion was 70.5% at one year and 64.9% at two years. Of the local failures, 11 occurred within the 95% isodose line (52.4%). Of these 11 in-field failures, 4 occurred early in practice with treatments of BED3 < 100 being delivered, which resulted in changes in institutional practice. We observed no grade 3 or greater toxicities in the acute (<3 months) or long-term setting. Of note, there were no fractures and over 50% received concurrent therapy.
Conclusion: This institutional experience demonstrates that SBRT can achieve 70.5% local control at one year with no grade 3+ toxicities, including no fractures: however, in-field failures in over 50% of recurrences suggest potential benefit from dose escalation strategies.