2234 - Separation Surgery Followed by Stereotactic Body Radiotherapy (24Gy in Two Fractions) for Metastatic Epidural Spinal Cord Compression: A Retrospective Study of 120 Patients

Purpose/Objective(s):

Although separation surgery followed by stereotactic body radiotherapy (SBRT) for metastatic epidural spinal cord compression (MESCC) has shown high and durable local control, no consensus has been established regarding the optimal dose. This study retrospectively evaluated the clinical outcomes of postoperative SBRT with 24 Gy in 2 fractions following separation surgery for MESCC.

Materials/Methods:

Patients with MESCC of Bilsky Grade (BG) = 1b who underwent postoperative SBRT (24 Gy in 2 fractions) following separation surgery between October 2013 and September 2025 were included. Patients with epidural space compression involving the cauda equina were also included down to the S2 level. Separation surgery was performed via a posterior approach, combined with spinal fixation and preoperative transarterial embolization. The dose constraints to the spinal cord (and cauda equina) (D_{0.035 cc}) were defined as 17 or 19.3 Gy for de novo and 11 or 12.2 Gy for re-irradiation patients. The primary endpoint was the 2-year LF, considering death as a competing risk; secondary endpoints included overall survival (OS) and treatment-related toxicity. In addition, various patient-, tumor-, and treatment-specific factors were evaluated for their potential predictive value for LF.

Results:

A total of 120 patients were analyzed. The median follow-up was 19 months (range, 3–111), and the median age was 64.5 years (range, 15–86). Thirty-six patients (30%) had a history of prior irradiation. Preoperative BG distribution was 1b/1c/2/3: 4/8/27/81, and postoperative BG was 1a/1b/1c/2/3: 2/39/16/37/26, with BG improvement in 62% and stable in 36% of patients. The 1- and 2-year LF rates were 10.7% and 18.5%, respectively. On univariate analysis (Gray’s test), spinal cord dose constraints (p < 0.001), prior irradiation (p = 0.03), and oligometastatic status (p = 0.03) were significantly associated with LF, pre- and postoperative BGs were not significant. Because spinal cord dose constraints were defined according to prior irradiation status, irradiation history was not included in the multivariable model to avoid overadjustment. On multivariate Fine–Gray analysis, spinal cord dose constraints (HR = 0.77, p < 0.001), and oligometastatic disease (HR = 2.64, p = 0.02) were significantly associated with LF (Table). The 1- and 2-year OS rates were 77.9% and 66.9%. Treatment-related toxicities included myelopathy in 1.7%, plexopathy in 3.3%, vertebral compression fracture in 17.5%, and hardware failure in 1.7% of patients.

Conclusion:

SBRT with 24 Gy in 2 fractions following separation surgery achieved excellent and durable local control in patients with MESCC. Spinal cord dose constraints were associated with local control.

Abstract 2234 – Table 1: Multivariate Fine–Gray Analysis for 2-year Local Failure

Table - Multivariate Fine–Gray Analysis for 2-year Local Failure
Variable	HR	95% CI	p value
Spinal cord dose constraint (D0.035cc)	0.77	0.67–0.89	< 0.001
Oligometastatic disease	2.64	1.16–6.02	0.02