Spinal reirradiation using the Cyberknife-preliminary efficacy from a single institution

via yyy60 on the Yahho MB:

>>Spinal reirradiation using the Cyberknife-preliminary efficacy from a single institution

Background: Spinal cord tolerance to prior radiation is a major limiting factor in reirradiating patients with spine metastases that have relapsed or progressed in a prior treated field due to concerns about toxicity. The accepted total tolerance dose of the spinal cord is approximately 5,000 cGy in conventional fractionation (180 cGy/day). This dose is reported to cause a 5% risk of myelitis.

Methods: 13 consecutive patients who had received prior external beam radiation to the spine and who were subsequently retreated with Cyberknife radiosurgery in 2005–2006 were reviewed. The radiation dose to the spinal cord and cauda equina given during the external beam and Cyberknife treatments were measured. The doses were also converted into 180 cGy equivalent doses using alpha/beta corrections and were also measured. Local control as measured by pre and post treatment imaging is reported.

Results: The median follow up was 9.1 months. The median external beam dose to the spinal cord was 3,811 cGy. The median fraction size was 238 cGy. The median prescribed dose using the Cyberknife for retreatment was 2,030 cGy. The median dose per fraction using the Cyberknife was 500 cGy. The median dose to 5% of the spinal cord (D05) from the Cyberknife was 1171 cGy. The median dose to the spinal cord converted to 180 cGy/day equivalent from the prior external radiation was 4,228 cGy. The median dose to the D05 of the spinal cord from the Cyberknife converted to 180 cGy/day equivalent was 1,641 cGy. The median total cumulative dose to the spinal cord from both external beam and Cyberknife was 5,171 cGy. The median total cumulative dose to the spinal cord from both external beam and Cyberknife converted to 180 cGy/day equivalent was 5,889 cGy. Local control was achieved in 13/13 patients (100%) No patients suffered from treatment related complications from the retreatment of the spinal cord.

Conclusions: Cancer patients with recurrent or progressive disease after prior external beam radiation can be safely retreated using the Cyberknife. Cyberknife radiosurgery provides local control and minimal risk of radiation induced myelopathy during the patient's lifetime. Cyberknife should be considered a safe treatment option for retreating patients who have relapsed or progressed in the treated spine after prior external beam radiation.