CyberKnife radiotherapy for orbital metastases : a single-center experience on 24 lesions

OBJECTIVES: To evaluate the feasibility, in terms of acute toxicity and symptom control, of CyberKnife (Accuray, Sunnyvale, CA)-based stereotactic radiotherapy (CyberKnife-SRT) for metastatic orbital lesions. METHODS: This retrospective study included patients with symptomatic metastases wholly located within the orbit. Palliative radiation treatment was performed using CyberKnife image-guided technology. Gross tumor volume was defined on a pre-radiotherapy magnetic resonance imaging. Acute and late toxicity was recorded according to Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer Scale. RESULTS: Between April 2012 and July 2016, 21 patients underwent CyberKnife-SRT for 24 orbital metastases from different primary tumors. Median treatment dose was 18 Gy (15-24 Gy) given in a median of 3 fractions (2-3 fractions) with a median dose of 6 Gy/fraction (5-10 Gy/fraction). Acute grade 1 toxicity was observed in eight cases. No local recurrence occurred after median follow-up of 6.2 months (1.1-30.0 months) among 16 lesions that underwent post-stereotactic radiotherapy magnetic resonance imaging. All patients reported decreasing pre-stereotactic radiotherapy symptoms without late toxicity. Follow-up >6 months (median 22.8 months) was available for nine lesions; complete and partial radiological response was registered in four and five of them, respectively. CONCLUSION: In our experience, CyberKnife-SRT is a well-tolerated treatment that offers high local and symptom control in patients with intraocular and periocular malignant lesions.