Multi-fraction stereotactic body radiotherapy for spinal metastases.

INTRODUCTION

Single-fraction stereotactic body radiotherapy (SBRT) has demonstrated efficacy in the management of spinal metastases. This study sought to investigate the role of multi-fraction spine SBRT in managing metastatic spinal tumors, particularly for tumors large in volume, compressing the spinal cord, or previously irradiated with conventional external beam radiotherapy (EBRT).

METHODS

Overall, 146 treatments were analyzed from a prospectively maintained spine SBRT database from 2002 to 2024. Treatments were excluded for missing baseline imaging or less than 1 month of follow-up. The most prescribed fractionation schemes were 24 Gy/2 fractions, 24 Gy/3 fractions, and 30 Gy/5 fractions. The median tumor volume was 40 cc (IQR: 18–79). Tumors were previously irradiated with EBRT (108 tumors, 74%), and most had epidural tumor extension (109 tumors, 75%).

RESULTS

The median follow-up was 9 months (IQR: 2–17). Eighteen (12%) tumors exhibited local tumor progression with local tumor control (LTC) rates of 89%, 84%, and 78% at 6-, 12-, and 24- months following SBRT. Lytic lesions (HR: 8.63, 95%CI: 1.11–67.3, p = 0.040) and tumors spanning > 1 vertebral level (HR: 2.76, 95%CI: 1.02–7.46, p = 0.046) were significantly associated with worsened LTC. Pain improvement or stability was noted for 93%, 89%, and 87% of treated cases at 1-, 3-, and 6-months post-SBRT. The median overall survival (OS) was 13 months with KPS ≤ 80 (HR: 0.41, 95%CI: 0.26–0.64, p < 0.001) and radioresistant primary tumor histology (HR: 0.50, 95%CI: 0.31–0.80, p = 0.004) being associated with worsened OS. The crude vertebral compression fracture development rate was 9%.

CONCLUSION

Multi-fraction spine SBRT is safe and effective for large spinal metastatic tumors, including those previously irradiated with EBRT.