Efficacy and safety of different fractions in stereotactic body radiotherapy for spinal metastases: A systematic review

Background In the treatment of spinal metastases, stereotactic body radiotherapy (SBRT) delivers precise, high-dose radiation to the target region while sparing the spinal cord. A range of doses and fractions had been reported; however, the optimal prescribed scheme remains unclear. Methods Two reviewers performed independent literature searches of the PubMed, EMBASE, Cochrane Database, and Web of Science databases. Articles were divided into one to five fractions groups. The Methodological Index for Non-randomized Studies (MINORS) was used to assess the quality of studies. Local control (LC) and overall survival (OS) were presented for the included studies and a pooled value was calculated by the weighted average. Results The 38 included studies comprised 3,754 patients with 4,731 lesions. The average 1-year LCs for the one to five fractions were 92.7%, 84.6%, 86.8%, 82.6%, and 80.6%, respectively. The average 1-year OS for the one to five fractions were 53.0%, 70.4%, 60.1%, 48%, and 80%, respectively. The 24 Gy/single fraction scheme had a higher 1-year LC (98.1%) than those of 24 Gy/two fractions (85.4%), 27 Gy/three fractions (84.9%), and 24 Gy/three fractions (89.0%). The incidence of vertebral compression fracture was 10.3%, with 10.7% in the single-fraction group and 10.1% in the multi-fraction group. The incidence of radiation-induced myelopathy was 0.19%; three and two patients were treated with single-fraction and multi-fraction SBRT, respectively. The incidence of radiculopathy was 0.30% and all but one patient were treated with multi-fraction SBRT. Conclusions SBRT provided satisfactory efficacy and acceptable safety for spinal metastases. Single-fraction SBRT demonstrated a higher local control rate than those of the other factions, especially the 24 Gy dose. The risk of vertebral compression fracture (VCF) was slightly higher in single-fraction SBRT and more patients developed radiculopathy after multi-fraction SBRT.