30 Gy in 4 Stereotactic Body Radiotherapy Fractions for Complex Spinal Metastases: Mature Outcomes Supporting This Novel Regimen

Abstract

BACKGROUND AND OBJECTIVES: We designed a 30 Gy in 4 fractions stereotactic body radiotherapy protocol, as an alternative option to our standard 2-fraction approach, for primarily large volume, multilevel, or previously radiated spinal metastases. We report imaging-based outcomes of this novel fractionation scheme. METHODS: The institutional database was reviewed to identify all patients who underwent 30 Gy/4 fractions from 2010 to 2021. Primary outcomes were magnetic resonance–based vertebral compression fracture (VCF) and local failure per treated vertebral segment. RESULTS: We reviewed 245 treated segments in 116 patients. The median age was 64 years (range, 24-90). The median number of consecutive segments within the treatment volume was 2 (range, 1-6), and the clinical target volume (CTV) was 126.2 cc (range, 10.4-863.5). Fifty-four percent had received at least 1 previous course of radiotherapy, and 31% had previous spine surgery at the treated segment. The baseline Spinal Instability Neoplastic Score was stable, potentially unstable, and unstable for 41.6%, 51.8%, and 6.5% of segments, respectively. The cumulative incidence of local failure was 10.7% (95% CI 7.1-15.2) at 1 year and 16% (95% CI 11.5-21.2) at 2 years. The cumulative incidence of VCF was 7.3% (95% CI 4.4-11.2) at 1 year and 11.2% (95% CI 7.5-15.8) at 2 years. On multivariate analysis, age ≥68 years (P = .038), CTV volume ≥72 cc (P = .021), and no previous surgery (P = .021) predicted an increased risk of VCF. The risk of VCF for CTV volumes <72 cc/≥72 cc was 1.8%/14.6% at 2 years. No case of radiation-induced myelopathy was observed. Five percent of patients developed plexopathy. CONCLUSION: 30 Gy in 4 fractions was safe and efficacious despite the population being at increased risk of toxicity. The lower risk of VCF in previously stabilized segments highlights the potential for a multimodal treatment approach for complex metastases, especially for those with a CTV volume of ≥72 cc.

Determining patients with spinal metastases suitable for surgical intervention: A cost‐effective analysis

“…Third, while comparing the cost‐effectiveness of surgery versus EBRT, it is important to consider stereotactic body radiotherapy (SBRT) as an alternative for ambulatory patients with metastatic epidural canal compromise from radiosensitive tumors and stable spinal conditions. SBRT has shown superiority over EBRT in pain relief and local tumor control, 48–50 potentially narrowing the cost‐effectiveness difference between surgery and radiotherapy. However, only 7.2% (200/2768) of patients received SBRT, presenting difficulties in executing a stratified analysis within this study.…”

Optimizing Clinical Implementation of Hypofractionation: Comprehensive Evidence Synthesis and Practical Guidelines for Low- and Middle-Income Settings

“…Remarkably, 54% of the patients had received at least one previous course of radiotherapy, and 31% had undergone previous spine surgery at the treated segment. Despite the population being at an increased risk of toxicity, the 30 Gy in four fractions regimen proved safe and efficacious in 24 months, warranting a randomized clinical trial to further evaluate its potential benefits [130].…”