Stereotactic body radiotherapy for spinal metastases: current status, with a focus on its application in the postoperative patient

Abstract

Stereotactic body radiotherapy (SBRT) for spinal metastases is an emerging therapeutic option aimed at delivering high biologically effective doses to metastases while sparing the adjacent normal tissues. This technique has emerged following advances in radiation delivery that include sophisticated radiation treatment planning software, body immobilization devices, and capabilities of detecting and correcting patient positional deviations with imageguided radiotherapy. There are limited clinical data specifically supporting the role of SBRT as a superior alternative to conventional radiation in the postoperative patient. The focus of this review was to examine the evidence pertaining to spine SBRT in the treatment of spinal metastases and to provide a comprehensive analysis of published patterns of failure, with emphasis on the postoperative patient.

Intensity‐modulated radiotherapy versus proton radiotherapy versus carbon ion radiotherapy for spinal bone metastases: a treatment planning study

“…Patients could benefit from hypofractionated or single‐fraction schedules 10 , 11 , 12 . Outcome data show high rates of local control and pain control for spine metastases treated with SBRT, and suggest better efficacy than with conventional palliative radiotherapy 11 , 13 , 14 …”

A Multinational Report on Methods for Institutional Credentialing for Spine Radiosurgery

“…In conventional fractionated radiotherapy that does not employ image-guidance, the number of fractions can range anywhere from 5 to 25, and the individual dose per fraction is smaller than with SBRT [24]. Compared to conventional fractionated radiotherapy, the steep dose gradients and tight margins achieved with spine SBRT have an even greater probability to lead to detrimental consequences via either a reduced tumor control or an increase in normal tissue toxicity [25].…”

“…While there has been a long history and great experience with frame based intracranial radiosurgery using a variety of technologies at institutions around the world, there is far less experience with the adoption of these frameless extracranial radiosurgery technologies. The term SBRT implies high-dose-perfraction radiation (typically > 5 Gy per fraction) delivered to an image-guided target in 1 to 5 fractions by using conformal radiation techniques [24]. SBRT for the spine is technically demanding because it often requires near-rigid body immobilization, sophisticated treatment planning allowing for sharp dose gradients, and imaging guidance to ensure that the dose is delivered accurately.…”

Current Status And The Future Of Spine Radiosurgery

“…In the past, we simply delivered a dose of radiation aimed to achieve short term pain relief without the intention of long-term local tumor and pain control. The doses of 20 Gy in 5 fractions, 30 Gy in 10 fractions and 8 Gy in 1 fraction are most common, and were chosen based on the limiting factor of spinal cord tolerance.With advances in radiation technology that includes sophisticated body immobilization devices, intensity modulated radiotherapy (IMRT), image-guided radiotherapy (IGRT) and robotic technology we are now able to dose escalate spinal metastases, and deposit 2 to 6 times the biologically effective dose as compared to conventional radiation while still sparing the spinal cord to a safe dose [1,2]. Spine SRS is based on routinely treating with 16-24 Gy in 1 fraction, 24 Gy in 2 fractions, and 24-30 Gy in 3 fractions, with the intent to improve long-term local tumor control rates and increase the rate of both complete pain relief and long-term pain control [2,3].…”

“…There are now evidence-based guidelines for spinal cord tolerance specific to spine SRS for both radiation naive and re-irradiated patients that can guide safe practice [6,7], we are learning about dose limits for the esophagus with single fraction SRS [10], and also predictors of VCF with respect to dosimetric and anatomic factors that may help select patients for stabilization prior to, or after, SRS [9]. Ultimately the patient can now be better informed as to the risks of spine SRS.With respect to the current clinical evidence supporting efficacy, the indications for spine SRS can be broken down into those who are radiation naive, those with prior radiation requiring salvage SRS for tumor progression, and patients who are post-operative and require adjuvant radiotherapy [2]. The outcomes for each of these cohorts have been summarized in recent reviews and overall demonstrate efficacy [2,11].…”