Delayed radiation-induced myelopathy after spinal radiosurgery

Area of Science:

• Neurology
• Radiation Oncology
• Neurosurgery

Background:

• Spinal cord injury is a feared complication of radiotherapy, often limiting treatment aggressiveness for spinal tumors.
• Radiosurgery offers a precise treatment modality, but understanding its potential complications like delayed myelopathy is crucial.

Purpose of the Study:

• To report a case series of patients who developed delayed myelopathy after spinal radiosurgery.
• To analyze clinical and dosimetric factors associated with radiation-induced myelopathy following spinal radiosurgery.

Main Methods:

• Retrospective review of 1075 patients treated with CyberKnife robotic radiosurgery for spinal tumors between 1996 and 2005.
• Prospective clinical and radiographic follow-up assessments.
• Identification of six patients who developed delayed radiation-induced myelopathy.

Main Results:

• Six patients (5 women, 1 man; mean age 48 years) developed delayed myelopathy at a mean of 6.3 months post-treatment.
• Tumors treated included 3 metastatic and 3 benign, with locations in the upper to midthoracic and cervical spine.
• Half of the patients with myelopathy received spinal cord biological equivalent doses exceeding 8 Gy; specific predictive dosimetric factors were not identified.

Conclusions:

• Delayed myelopathy is uncommon with current radiosurgery dose schedules.
• Radiation injury occurred across a spectrum of doses, preventing identification of specific contributing dosimetric factors.
• Recommend limiting spinal cord treatment volume to below an 8-Gy equivalent dose to mitigate myelopathy risk.