Postoperative Epidural Disease and Local Control after Separation Surgery and Spine Stereotactic Body Radiation Therapy.

Abstract

Limited data are available on outcomes of patients with spinal metastases treated with separation surgery with postoperative stereotactic body radiation therapy (SBRT). This is a retrospective cohort study of 497 patients treated to 532 lesions between 2013-2024. We evaluated local failure (LF) and adverse events (hardware failure [HF] requiring surgical intervention, radiation myelitis [RM] and vertebral compression fracture [VCF]). Incidences of LF, VCF, RM, and HF were analyzed considering death as a competing risk. Dosimetric variables, including minimal biological effective dose to the clinical target volume (CTV Dmin BED10) were obtained. Preoperative and postoperative epidural spinal cord compression (ESCC) scores were calculated based on preoperative MRI and postoperative myelogram simulation. Median follow-up time among surviving patients was 74.5 months (95% CI 70-94). Median overall survival was 14 months (95% CI 13-17). The risk of LF (95% CI) at 1, 2, and 3 years was 7.7% (5.6-10%), 10% (7.9-13%), and 13% (10-16%), respectively. At 2 years, cumulative incidences of VCF, RM, and HF requiring surgery were 2% (95% CI, 1-3.5%), 1% (0.39-2.3%), and 3.8% (2.4-5.8%), respectively. On univariable and multivariable regression, CTV Dmin BED10 correlated with risk of LF (on multivariable regression, hazard ratio 0.96, 95% CI 0.93-0.99, p = 0.005). After excluding previously radiated lesions, postoperative ESCC ≤1C was associated with an approximately 2-times higher likelihood of achieving the median CTV Dmin BED10 than ESCC 2 (OR: 2.06, 95% CI 1.31-3.26, p=0.002), whereas a postoperative ESCC ≤1B was not associated with higher odds of achieving the median CTV Dmin BED10 compared to ≥1C (OR: 0.75, 95% CI 0.50-1.11, p=0.15). In this large series of separation surgery followed by spine SBRT, local control was excellent with few adverse events. Higher CTV minimum biological dose-enabled by postoperative ESCC ≤1C -was the strongest predictor of durable local control.