A case series and review of stereotactic body radiation therapy for contiguous multilevel spine metastases.

Purpose: A majority of published series report on stereotactic body radiation therapy (SBRT) for 1-2 contiguous vertebral levels due to concerns regarding setup accuracy and radiation toxicity. This study evaluates patients with metastases spanning ≥ 3 contiguous levels treated with SBRT and augments its findings with a review of other studies investigating multilevel spine SBRT.

Methods: Analysis of a prospectively collected database of 49 patients with 55 metastases spanning ≥ 3 contiguous vertebral levels treated with SBRT at a single institution (2002-2023) was performed. Outcomes identified included local failure (LF), pain response, overall survival, and toxicity. The median single-fraction prescription dose was 15 Gy (range: 8-18); multifractionated treatment utilized prescription doses of 18-30 Gy in 2-5 fractions.

Results: Median follow-up was 7 months (range: 1-103). The 6-month, 1-year, and 2-year cumulative incidence rates of LF were 7%, 11%, and 11%, respectively. No prognostic factors were associated with LF. Pain was reported to improve or remain stable for 49 lesions (89%). Ten adverse radiation events (18%) were identified; pain flare (5%), dermatitis (4%), and vertebral compression fracture (VCF, 9%). The 3-month, 6-month, and 1-year cumulative incidence rates of VCF were 4%, 7%, and 7%, respectively. No instances of esophageal toxicity or myelopathy were observed.

Conclusions: This study of multilevel SBRT is one of the largest to investigate outcomes in this challenging clinical scenario. Spine SBRT confers low rates of LF and toxicity for patients with multilevel disease, which was previously considered a relative contraindication. Spine SBRT may be considered in this patient population instead of low-dose palliative RT.