Spinal radiosurgery has long posed difficult problems for oncologists and neurosurgeons. Due to the close proximity of sensitive structures like the spinal cord, traditional radiation treatments were not accurate enough. In addition, since skeletal structures such as spinal vertebra do move independently, clinicians were required to surgically implant fiducials into the spine in order to track the movement of the lesion during treatment, which introduced all the drawbacks associated with invasive surgery. Prior to the introduction of the CyberKnife System, patients had few options and little hope for tumours that could not be surgically removed.
"Spinal Radiosurgery treatments require superior precision throughout the entire procedure. Relying only on image guided patient set-up is not enough. You must have the ability to continually track and correct for motions of the spine throughout treatment because in our experience patients do move after set-up is complete", stated Steve Chang M.D., Assistant Professor, Department of Neurosurgery at Stanford University Medical Center.
Primary benign spine tumours are uncommon and make up less than 5 percent of bone tumours. Many however are in difficult to reach locations and can develop within the substance of the spinal cord itself and disrupt neurological function in the spinal cord. Metastatic disease of the spine is much more common. Approximately 40 to 80 percent of patients who die from cancer have bony metastases at the time of death, with the spine being the most common site for skeletal metastases.
The primary rationale for treating spinal metastases is the relief of pain and halting further deterioration of the spine. CyberKnife, because of its accuracy, can often treat spine tumours that are deemed inoperable by directing high doses of radiation without damaging adjacent normal tissue. Spine tumours most commonly treated with CyberKnife include: meningioma, schwannoma, neurofibroma, hemangioblastoma, arteriovenous malformations, chondrosarcoma, chordoma, ependyoma, spinal metastases from many sources, myeloma, lymphoma, and Ewing sarcoma.
The CyberKnife Radiosurgery System is the only system in the world that continually tracks lesions and automatically compensates for their movements throughout the entire treatment. Only the CyberKnife is capable of delivering sub-millimeter total clinical accuracy, now in the spine without fiducials, thus offering unparallel precision and conformality.
"Xsight obviates the need for placement of fiducials and allows for computerized real-time tracking and delivering of radiation with sub-millimeter accuracy. For those wishing to irradiate tumours of the spine this represents a major breakthrough", remarked Fraser Henderson M.D., Director, Spine Tumour Center, Georgetown University Hospital. Additionally, he stated: "This is a significant advance in eliminating pain for the patient and for allowing the surgeon to expedite treatment within the limited therapeutic window."
The Xsight Spine Tracking System, developed by CyberKnife manufacturer Accuray, relies on the bony anatomy of the spine to automatically locate and track tumours along the spinal column. Patients with spinal tumours now receive a computerized tomography (CT) scan, the results are downloaded into the Xsight software, and the system creates a highly detailed measurement grid for the CyberKnife to follow. This non-invasive system enables neurosurgeons, radiation oncologists and medical physicists to easily treat cancerous and benign tumours without implanting fiducials.
Euan Thomson, Ph.D., President and CEO of Accuray Incorporated, stated: "The Xsight Tracking System represents one of the most significant technology developments in non-invasive surgery in many years. Finally, patients with spinal lesions can benefit from the unparalleled accuracy and effectiveness of CyberKnife radiosurgery completely free of fiducials and implantation procedures. While fiducials were a superior alternative to rigid external frames, they were still time consuming for caregivers and uncomfortable for patients. We are delighted that the Xsight Spine Tracking System has proven to be such a success in initial treatments."
The world's first non-invasive tracking system for spinal radiosurgery, Xsight is effective for treating lesions throughout the spinal region including cervical, thoracic, lumbar and sacral tumours. During its limited release, more than 60 patients have been treated with the CyberKnife System with Xsight, adding to the more than 1600 spine radiosurgery cases that have been treated with the CyberKnife over the past four years. Xsight is just another example of how the CyberKnife System expands the practice of radiosurgery by offering a non-invasive cost effective alternative to surgery.
The CyberKnife Stereotactic Radiosurgery System is a non-invasive, 100 percent frameless image-guided radiosurgery system that ablates tumours and other lesions anywhere in the body without invasive surgery. The CyberKnife System treats in single or staged - typically 2-5 - sessions, and monitors internal reference points in the anatomy - skeletal landmarks or small implanted markers - to correct for patient movement in real time during actual treatment.
It delivers multiple beams of precisely directed radiation that converge upon the tumour while minimizing injury to surrounding healthy tissue. It is the only system in the world that integrates real-time image guidance and robotic delivery of radiation to deliver proven sub-millimeter "total clinical accuracy".
The unique CyberKnife technology was developed in co-operation with Stanford University. The CyberKnife is 510(k) cleared by the FDA in the United States and has CE approval in Europe to treat anywhere in the body where radiation treatment is indicated. With over 100 peer-reviewed publications supporting its clinical practice the CyberKnife System has treated over 12.500 patients worldwide.
Located in Sunnyvale, California, Accuray is a privately held corporation dedicated to revolutionizing the treatment of lesions and tumours anywhere in the body by the precise delivery of high doses of radiation using the CyberKnife Stereotactic Radiosurgery System. Through the development and marketing of the CyberKnife System, and participation in ongoing clinical research at prominent hospitals, Accuray and its customers are making stereotactic radiosurgery a viable and accessible option for cancer patients worldwide. More CyberKnife news can be found in the VMW February 2005 article Mississippi Baptist and Georgetown University Hospital to acquire Accuray's CyberKnife System.