Reference: Update February 2026 | Issue 2 | Vol 12 | Page 47
Stereotactic body radiotherapy (SBRT) is an established treatment for previously unirradiated spinal metastases, however, the literature is limited with respect to SBRT as a re-irradiation salvage therapy.
Effective salvage treatment of previously irradiated spinal metastases represents a critical clinical challenge. Spine SBRT is an attractive option in this scenario as it allows for dose escalation.
Last month, for the first time, the European Society for Radiotherapy and Oncology (ESTRO) and the International Stereotactic Radiosurgery Society (ISRS) issued joint clinical guidelines for re-irradiation of spinal metastases with SBRT. The guidelines offer clinicians much needed clarity in this area.
The recommendations are based on a systematic review and meta-analysis of papers published between January 2006 and September 2024 that reported on the clinical outcomes of at least five patients treated with spine SBRT re-irradiation (≥5 Gy per fraction) for vertebral metastases.
The intention was to provide insight into three key questions:
1) Is SBRT re-irradiation effective in pain control for painful vertebral metastases?
2) Is SBRT re-irradiation effective in local control for vertebral metastases?
3) What is the toxicity profile of spine SBRT re-irradiation?
After the initial article screen, 20 studies (five prospective, 15 retrospective) met the inclusion criteria for analysis. A total of 1,538 spine metastases were treated in 1,284 patients. The median re-irradiation dose was 24 Gy in two fractions (range: 16-30 Gy in 1-5 fractions) after a median 30 Gy in 10 fractions of prior conventional radiotherapy.
Vertebral compression fracture, nerve root damage, and myelopathy events were observed in a pooled proportion of 5 per cent, 5.6 per cent, and 1.7 per cent, respectively.
The consensus was that for painful spinal metastases, salvage SBRT shows promising results in terms of pain response, with a pooled overall response rate of 77 per cent and a complete response rate of 34 per cent. Only two studies reported on the median time to pain progression (13 and 12 months, respectively).
There was some evidence of SBRT superiority for pain outcomes, however, the guidelines committee stated that, ultimately, prospective randomised studies with precise baseline and post-treatment pain assessments are required to provide definitive evidence for re-irradiation spine SBRT with respect to superiority in pain outcomes.
With a median follow up of 12 months, the pooled one- and two-year local control (LC) rates were 81 per cent and 70 per cent, respectively.
1. Is SBRT re-irradiation effective in pain control for painful vertebral metastases?
▶ Spine SBRT re-irradiation results in effective pain control in patients with prior cEBRT.
▶ Pain assessment before SBRT re-irradiation and after treatment is strongly recommended using a standardised instrument such as the Brief Pain Inventory index (BPI), Visual Analogue Scale (VAS), or Numeric Rating Scale (NRS).
2. Is SBRT re-irradiation effective in local control for vertebral metastases?
▶ Spine SBRT re-irradiation results in effective local control with one- and two-year pooled local control rates of 81 per cent and 70 per cent, respectively.
▶ Spine re-irradiation with SBRT is associated with favourable local control and can be considered after prior conventional external-beam radiotherapy (cEBRT) or SBRT.
3. What is the toxicity profile of spine SBRT re-irradiation?
▶ Re-irradiation with SBRT results in low serious adverse event rates with the caveat of carefully considering SBRT in the elderly.
▶ Repeated SBRT to the same spine level is not associated with a higher risk of adverse events, when compared to SBRT after first course cEBRT.
TABLE 1: ESTRO-ISRS consensus statements for spine SBRT re-irradiation
Patient selection for SBRT re-irradiation of vertebral metastases:
▶ SBRT re-irradiation should be considered in carefully selected patients with longer term overall survival expectancy if a more durable pain response than can be provided by conventional radiotherapy is intended.
▶ SBRT for re-irradiation is recommended in carefully selected oligometastatic patients if durable local metastasis control is intended.
▶ SBRT is recommended only if the interval to the first radiotherapy course is >12 months. SBRT can be considered in carefully selected patients if the interval is between 6-12 months.
▶ A baseline SINS assessment of spinal stability is strongly recommended.
▶ SBRT is recommended only for stable or potentially unstable vertebral metastases (SINS 0-12).
▶ Prior surgery should not be considered as an exclusion criteria to SBRT.
Imaging and treatment planning for SBRT reirradiation of vertebral metastases:
▶ For SBRT re-irradiation of vertebral metastasis after prior radiotherapy, the use of previously reported ESTRO technical guidelines is recommended.
▶ MRI is strongly recommended for target volume and organs at risk delineation. If MRI imaging is not possible, it is recommended that CT myelography be carried out for spinal cord/thecal sac delineation and additional functional imaging such as PET to confirm target volume delineation.
▶ The use of highly-conformal intensity-modulated image-guided techniques (IMRT, VMAT, robotic radiotherapy) is strongly recommended.
Target and organ at risk doses for SBRT reirradiation of vertebral metastases:
▶ The following dose fractionations are recommended: 24 Gy/2 fx, 30 Gy/4 fx, 30 Gy/5 fx, or 16 Gy/1 fx.
▶ For SBRT re-irradiation of vertebral metastasis after prior radiotherapy, the use of the Hytec 2021 spinal cord dose constraints is recommended.
TABLE 2: Joint ESTRO ISRS clinical practice recommendations
Despite the low level of evidence, a consensus was reached after the first round of voting for 11 practice recommendations. There was a strong consensus to recommend the use of SBRT for spinal metastases re-irradiation for carefully selected patients with a longer life expectancy, where durable results – in terms of both pain response and disease local control – are required.
A strong consensus was also reached on the recommendation regarding a minimum time interval of 12 months from the previous radiation treatment to propose vertebral re-irradiation with SBRT. However, the possibility of evaluating SBRT re-irradiation in carefully selected patients remains if the time interval is 6-12 months.
The panel expressed a strong consensus regarding the necessity of a SINS evaluation before considering vertebral re-irradiation with SBRT, limiting eligibility to patients with a score of 0-12 (stable or potentially unstable).
Concurrent or prior vertebral surgery was also not considered to be an exclusion criterion for SBRT re-irradiation.
There was also strong consensus around the technical aspects of vertebral SBRT re-irradiation, particularly with the mandatory use of MRI for target volume and organs at risk (OARs) delineation. The guidance states that MRI can be substituted by myelography only in cases where MRI is not possible, adding that this approach requires integration with additional functional imaging such as PET for tumour delineation.
Reference
Alongi F, Cuccia F, Kotecha R, et al. ESTRO-ISRS clinical practice recommendations for re-irradiation of spinal metastases with stereotactic body radiotherapy: Delphi consensus supported by a systematic review and meta-analysis. Radiother Oncol. 2026 Jan;214:111304. doi: 10.1016/j.radonc.2025.111304.
