CT-myelography for high-dose irradiation of spinal and paraspinal tumors with helical tomotherapy: revival of an old tool.

Background And Purpose: High-dose irradiation or reirradiation of spinal and paraspinal tumors is a challenge particularly in the presence of metal artifacts after surgery. Image-guided advanced intensity-modulated radiotherapy delivers high-dose radiation to the tumor sparing the spinal cord. Precise delineation of the spinal cord is necessary treating para- and intraspinal tumors with a sufficient dose.

Patients And Methods: The use of myelo-CT was evaluated in 23 patients with spinal and paraspinal tumors. All patients had had previous surgery with metal implants in the radiation area. All patients had an indication for high-dose irradiation. Treatment planning was performed using nonenhanced and contrast-enhanced myelo-CT in the same position and immobilization and both CT scans were matched. Treatment was performed by using a tomotherapy treatment unit.

Results: Contouring of the myelon in all slices of the myelo-CT was possible in 20 of 23 patients. All these patients were treated with doses of median 69.4 Gy in 2 Gy/1.8 Gy single doses using daily image guidance. One patient received an integrated boost with a TD/SD of 70/2.3 Gy. No side effects have been observed so far during a median follow-up of 15.5 months. No separation between tumor and myelon could be observed in 3 patients.

Conclusion: Myelo-CT offers a distinct delineation of the myelon and the paraspinal tumor in case of artifacts due to metal implants after surgery. Using this tool in combination with advanced image guidance and IMRT techniques, patients with relatively radioresistent paraspinal tumors might have the chance of improved local control using higher target doses.