Fiducial-free CyberKnife radiosurgery for residual metastatic spinal tumor after decompression and instrumentation

Stereotactic spinal radiotherapy is a promising technology for use in the multidisciplinary management of benign and malignant spinal tumors. We present two patients with residual metastatic spinal tumors and their treatment with CyberKnife (Accuray, Sunnyvale, CA, USA) after decompression and instrumentation, one of which was successful and the other not. A 73-year-old male patient was admitted with bilateral extremity weakness (Grade IV) and voiding difficulty that had developed 2 days previously. CyberKnife treatment for the residual tumor after surgery with decompression and instrumentation was attempted, but could not be performed due to imaging interference caused by the instrumentation. A second patient, a 49-year-old male, was admitted with right extremity weakness and voiding difficulty that had developed 5 months previously. In this patient, we were able to perform CyberKnife treatment on the residual tumor after decompression and instrumentation. Based on these two patients, we believe that fiducial-free CyberKnife treatment is not suitable for treatment of residual metastatic spinal tumors at the upper thoracic levels, after decompression with instrumentation. This is due to the difficulties in matching digitally reconstructed radiographs with live radiographic images, as a result of the larger inclination and smaller vertebral body surface at the upper thoracic level. (C) 2012 Elsevier Ltd. All rights reserved.