Stereotactic body radiotherapy for spinal metastases: Retrospective analysis of a West Australian cohort.

Stereotactic body radiotherapy for spinal metastases: Retrospective analysis of a West Australian
cohort

Purpose: In recent years, stereotactic body radiotherapy (SBRT) has become a standard treatment for spinal metastases, particularly for oligometastatic or oligoprogressive disease where SBRT may represent a curative option or delay a change in systemic treatment [1]. In addition to better oncologic outcomes, randomised evidence shows that SBRT for spinal metastases provides superior pain control compared to standard palliative external beam radiotherapy [2]. Spine SBRT has been shown to be safe, with a reported 8.8% risk of vertebral compression fractures (VCF) and a myelopathy risk of <0.5% [1].
We sought to investigate the clinical outcomes and toxicity profile of spinal metastases treated with SBRT in a large West Australian cohort.

Methods and Materials: In this institutional research ethics board-approved study, we retrospectively reviewed data of patients treated with SBRT to spinal metastases at two centres in Western Australia from March 2018 to January 2022. All patients were discussed in a SBRT-focused peer review meeting.
Spinal lesions were treated with 24-27 Gy in 3 fractions (n=49), 30-35 Gy in 5 fractions (n=29) and 48 Gy in 10 fractions (n=3). Outcomes measured included the incidence of toxicities, the need for spinal stabilisation surgery, and local failure rates. Patients were followed up at 3-6 monthly intervals by radiation oncology and/or medical oncology with PET/CT or MRI.

Results: The total number of patients was 68, and the total number of spinal segments treated was 81 (8 cervical, 47 thoracic, 23 lumbar and 3 sacral). The median age was 72.5 (range 44-90), and 76% were male. The most common primary malignancies were prostate (54%), breast (13%) and lung (9%).
Indications for SBRT were ablation of oligometastatic or oligoprogressive disease (78%), or local control for pain relief (22%). Median spinal instability neoplastic score (SINS) prior to SBRT was 4 (range 0-13), and the most common Bilsky score was 0. The median follow-up time was 15.5 months (range 1-62), and
the local failure rate at 12 months was 3%. The cumulative incidence of VCF was 8.6%. 2 patients required spinal stabilisation surgery, and 1 patient required vertebroplasty. No patients developed myelopathy.

Conclusion: This retrospective analysis suggests that SBRT for spinal metastases using a 3 or 5-fraction regimen is a safe and effective treatment. Our findings add to the existing body of literature to support the utility of SBRT in managing spinal metastases. In future, we aim to introduce a 24 Gy in 2 fraction regimen at our centres [2].

References:
1. RS Guninski, Cuccia F, Alongi F, N Andratschke, Belka C, D Bellut, et al. Efficacy and safety of SBRT
for spine metastases: A systematic review and meta-analysis for preparation of an ESTRO practice
guideline. Radiotherapy and Oncology. 2023 Nov 1;109969–9.
2. Sahgal A, Myrehaug SD, Siva S, Masucci GL, Maralani PJ, Brundage M, et al. Stereotactic body
radiotherapy versus conventional external beam radiotherapy in patients with painful spinal metastases:
an open-label, multicentre, randomised, controlled, phase 2/3 trial. The Lancet Oncology. 2021
Jul;22(7):1023–33.