What Predicts the Prognosis of Spinal Metastases in Separation Surgery Procedures?

Background: Separation surgery is performed to provide a safe gap between the epidural tumor and spinal cord for postoperative stereotactic body radiotherapy (SBRT) in cases of spinal metastases. However, there is a gap in evidence regarding sufficient tumor resection in separation surgery. We describe the prognoses according to the extent of resection in separation surgery.

Methods: This retrospective study included 36 consecutive patients who underwent separation surgery and postoperative SBRT between December 2016 and December 2019 at a single center. Local control (LC), overall survival (OS), distance of separation (DS), and quality-of-life parameters were analyzed. P values <0.05 were considered statistically significant.

Results: Patients were assigned to the aggressive resection group (ARG, n = 18) or moderate resection group (MRG, n = 18), with estimated LC and OS at 1 year of 79.0% and 75.9%, respectively. There were no significant differences between ARG and MRG in estimated LC (85.9% vs. 72.2%; P = 0.317) or OS (69.3% vs. 80.9%, P = 0.953) at 1 year. All 5 patients in MRG who developed local progression had less satisfactory tumor resection with DS <3 mm. A borderline significant difference in estimated LC at 1 year was noted between individuals with DS <3 mm and those with DS ≥3 mm (51.9% vs. 100.0%; P = 0.053) in MRG. There was no statistical difference between ARG and MRG in quality-of-life parameters.

Conclusions: Moderate resection of ventral dural mass did not significantly reduce patients' prognosis in separation surgery. However, the minimal distance between the postoperative residual epidural tumor and spinal cord should be ≥3 mm.