Outcomes and toxicity for hypofractionated and single-fraction image-guided stereotactic radiosurgery for sarcoma metastatic to the spine.

Abstract

9501 Background: Conventional radiation treatment (20-40 Gy total dose, 5-20 fractions, 2-5 Gy per fraction) for sarcoma metastatic to the spine provides subtherapeutic doses and results in poor local control (58-77% at 1 year). Hypofractionated (HF) and/or single-fraction (SF) image-guided stereotactic radiosurgery (IG-SRS) may provide a more effective means of control and salvage for these lesions. Methods: Patients with pathologically-proven high-grade sarcoma metastatic to the spine treated with HF and SF IG-SRS were included. Local control (LC) and overall survival (OS) were analyzed using Kaplan-Meier statistics; univariate/multivariate analyses were performed using Cox regression. Toxicities were assessed according to CTCAE v4.0 criteria. Results: From 5/2005 and 11/2012, 88 patients with 120 discrete metastases were treated with HF (3-6 fractions, median dose 28.5 Gy; n=52, 43.3%) or SF IG-SRS (median dose 24 Gy, n=68, 56.7%). Median followup was 12.3 months. LC at 12 months was 87.9% (95% CI 81.3-94.5%). OS at 12 months was 60.6% (95% CI 49.6-71.6%) with a median survival of 16.9 months. SF IG-SRS demonstrated superior LC to HF IG-SRS (P=.007) (Table). SF IG-SRS retained its significance in terms of improved LC on multivariate analysis, HR 0.304 (95% CI: 0.117-0.790); variables tested included prior radiation therapy, histology, IG-SRS fractionation, surgery, and chemotherapy. Treatment was well-tolerated with 1% acute Grade 3 toxicity and 4.5% chronic Grade 3 toxicity observed; there were no > Grade 3 toxicities. Conclusions: In the largest series of metastatic sarcoma to the spine to date, image-guided stereotactic radiosurgery provides excellent local control in the setting of an aggressive disease with low radiation sensitivity and poor prognosis. Single-fraction image-guided stereotactic radiosurgery demonstrates the highest rates of local control with minimal toxicity. [Table: see text]