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.

[BACKGROUND] 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. We performed a systematic review and meta-analysis as basis for joint ESTRO-ISRS clinical practice recommendations of salvage SBRT for spinal metastases.

[METHODS] A systematic review and meta-analysis were performed using PRISMA methodology, including publications from January 2006 to September 2024, reporting on the clinical outcomes of ≥ 5 patients treated with spine SBRT re-irradiation (≥5 Gy per fraction) for vertebral metastases. These data served as basis for joint ESTRO-ISRS clinical practice recommendations.

[RESULTS] After the initial article screen, 20 studies (5 prospective, 15 retrospective) met the inclusion criteria for analysis. A total of 1538 spine metastases were treated in 1284 patients. The median re-irradiation dose was 24 Gy in 2 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 5.0 %, 5.6 %, and 1.7 %, respectively. With a median follow-up of 12 months, the pooled 1- and 2-year LC rates were 81 % (95 % CI: 77-86 %) and 70 % (95 % CI: 61-79 %), respectively. Despite the low level of evidence, a consensus was reached after the first round of voting for 11 practice recommendations, suggesting a substantial level of agreement among the experts.

[CONCLUSIONS] Re-irradiation with SBRT for spine metastases following prior conventional radiation or SBRT was efficacious, safe, and is a recommended treatment option in appropriately selected patients. Joint practice recommendations are provided on behalf of ESTRO and ISRS to guide clinical practice.