The role of stereotactic body radiotherapy and stereotactic radiosurgery in the re-irradiation of metastatic spinal tumors

Abstract

Stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) are advanced radiotherapy delivery techniques that allow for the delivery of high-dose per fraction radiation. Advances in imaging technology and intensity modulation have allowed SRS and SBRT to be used for the treatment of tumors in close proximity to the spinal cord and cauda equina, in particular spinal metastases. While the initial treatment of spinal metastases is often conventional palliative radiotherapy, treatment failure is not uncommon, and conventional re-irradiation may not be feasible due to spinal cord tolerance. SBRT and SRS have emerged as important techniques for the treatment of spinal metastases in the proximity of previously irradiated spinal cord. Here we review the current data on the use of SBRT and SRS spinal re-irradiation, and future directions for these important treatment modalities.

Keywords::

• re-irradiation
• spinal cord tolerance
• spinal metastases
• stereotactic body radiotherapy
• stereotactic radiosurgery

Financial & competing interests disclosure

Y Yamada is a member of the Institute for Medical Education Speakers Bureau, a consultant for Varian Medical Systems and a consultant for the International Atomic Energy Agency. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) are powerful technologies that allow high-dose per fraction radiation therapy delivery.

• SBRT spinal re-irradiation data demonstrate high rates of local control, effective pain palliation and neurological symptom improvement.

• Effective in radioresistant histologies such as renal cell carcinomas, melanomas and non-small-cell lung carcinomas.

• Limited understanding of partial volume and cumulative spinal cord tolerance to re-irradiation.

• Significant variability in treatment techniques, contouring methods and dose-reporting prevent effective comparison of different experiences.

• Toxicities can be significant including radiation myelopathies and vertebral compression fractures, warranting close observation of these patients.

• Surgery can play an important role in the delivery of SBRT spinal re-irradiation by creating separation from the target and spinal cord.

• Role for SBRT re-irradiation in setting of systemic therapies is unknown and remains to be elucidated.

• Future prospective and/or randomized trials with standardized dosimetric reporting methods will be valuable in shaping the future experience of SBRT spinal re-irradiation.

Notes

The classic radioresistant histologies in the experience of stereotactic radiosurgery and stereotactic body radiotherapy are renal cell carcinoma and melanoma.