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Achieving Integrated, Collaborative Management of Spinal Tumors using CT Myelography based Stereotactic Radiosurgery Planning: A Preliminary Experience 2014

Category Interventional Vahe M. Zohrabian
Zain A. Husain
Maxwell Laurans
Veronica L. Chiang
Amit Mahajan
Michele H. Johnson
Purpose The majority of spinal tumors are metastatic in nature, with approximately 18,000 new cases diagnosed yearly. In addition to surgical decompression, radiation plays an important role in local control, although the main challenge lies in balancing maximal tumoricidal dose and minimizing radiation injury. New techniques such as intensity-modulated radiation therapy (IMRT), in combination with imaging guidance, allow for increased radiation dose in a safe manner, although no consensus exists regarding planning or treatment. CT Myelography has been employed to distinctly delineate neural structures, allowing for precise treatment of tumor with high-dose irradiation. Here, we discuss collaborative efforts between the Departments of Diagnostic Radiology, Radiation Oncology, and Neurosurgery in the creation of a robust spine stereotactic radiosurgery pre-treatment planning program at a large cancer center designed to increase patient throughput and enhance therapeutic accuracy. Materials & Methods In November 2012, a spine tumor board was created to review patients with metastatic disease to the spine and to explore a variety of treatment options, including conventional radiation therapy, chemotherapy, stereotactic radiosurgery, minimally invasive and conventional surgery, vertebral augmentation with vertebroplasty/kyphoplasty, and palliative care. The enhancement of the spine radiosurgery program was largely sought because of increasing numbers of patients with spinal metastatic disease and the difficulty of acquiring efficient co-registration from MRI and CT simulation scan data sets with conventional radiation planning. In cases where tumor closely approximated radiosensitive neural structures, a decision was made to obtain CT Myelography for pretreatment planning. Calibration between the diagnostic radiology CT and radiation oncology simulation CT were evaluated and documented by both diagnostic and therapeutic radiology physicists. Electronic transfer of data from the diagnostic radiology CT scanner to the radiation oncology simulation CT was also tested and found to be successful. Results Patients were scheduled for CT Myelography-based simulation approximately 1 week prior to treatment. The patient arrived in the Diagnostic Radiology department as the first case in the morning. Patient registration, chart review, consent, and IV access were performed, and the patient was on the table within one hour of arrival. A lumbar puncture was performed with instillation of a standard dose of 20 mL of Omnipaque 180 into the thecal sac to opacify the subarachnoid space. Approximately 1-3 mL of CSF fluid was obtained for analysis in each patient. Contrast was advanced into the area of interest and fluoroscopic spot films obtained. For tumors in the thoracic area, a gold fiducial localization marker was placed to provide an internal fiducial for correlation with the external fiducials and the immobilization bag. The spinal needle was removed and the patient was immediately transported across the hall to a CT scanner with flat table top. There, the radiology and radiation oncology technologists met the patient, and the patient was immobilized in a pre-molded standard mask system or stereotactic body frame system utilizing double-vacuum technology to provide motion stability. The patient was then positioned on the CT table and scanned using a 60-65 cm FOV to include the immobilization device, and the images checked by the radiologist for diagnostic quality. The CT Myelographic dataset was subsequently reformatted with a smaller field of view and thin sections, including sagittal and coronal reconstructions, for diagnostic interpretation. Following this, the patient was taken to the diagnostic radiology recovery area for monitoring for 1-2 hours following the procedure prior to home discharge. The pretreatment CT imaging was immediately available to the radiation oncologist and neurosurgeon for treatment planning utilizing inverse planning IMRT software. Conclusion We performed CT Myelography pretreatment planning in 20 patients between December 2012 and December 2013. None of the patients in our series experienced radiation myelitis or compression fractures as a complication of radiosurgery. We have documented tumor type and primary vs. recurrent, time from initial consult to pretreatment planning CT Myelogram, time from CT planning stage to radiation treatment, and mean radiosurgical doses. Our overall experience has been positive, and has fostered a close working relationship between the radiologists, oncologists, and neurosurgeons, which we expect to translate into improved clinical outcomes. References Shiu AS, Chang EL, Ye JS, et al. Near simultaneous computed tomography image-guided stereotactic spinal radiotherapy: an emerging paradigm for achieving true stereotaxy. Int J Radiat Oncol Biol Phys. 2003 Nov 1;57(3):605-13. Thariat J, Castelli J, Chanalet S, et al. CyberKnife stereotactic radiotherapy for spinal tumors: value of computed tomographic myelography in spinal cord delineation. Neurosurgery. 2009 Feb;64(2 Suppl):A60-6. Uhl M, Sterzing F, Habl G, et al. CT-myelography for high-dose irradiation of spinal and paraspinal tumors with helical tomotherapy: revival of an old tool. Strahlenther Onkol. 2011 Jul;187(7):416-20.