Impact of Postoperative Stereotactic Body Radiation Therapy on Survival of Patients with Spinal Metastases in the Context of Additional Systemic Adjuvant Therapy

Stereotactic body radiotherapy (SBRT) has been established as a safe and effective treatment modality for control of long-term pain and tumor growth. However, few studies have investigated the efficacy of postoperative SBRT versus conventional external beam radiation therapy (EBRT) in extending survival within the context of systemic therapy. A retrospective chart review of patients who underwent surgery for spinal metastasis at our institution was conducted. Demographic, treatment, and outcome data were collected. SBRT was compared with EBRT and non-SBRT, and analyses were stratified by whether patients received systemic therapy. Survival analysis was conducted using propensity score matching. Bivariate analysis in the nonsystemic therapy group revealed longer survival with SBRT compared with EBRT and non-SBRT. Further analysis also showed that primary cancer type and preoperative mRS significantly affected survival. Within patients who received systemic therapy, overall median survival for patients receiving SBRT was 22.7 months (95% confidence interval [CI] 12.1–52.3) versus 16.1 months (95% CI 12.7–44.0; P = 0.28) for patients who received EBRT and 16.1 months (95% CI: 12.2–21.9; P = 0.07) for patients without SBRT. Within patients who did not receive systemic therapy, overall median survival for patients with SBRT was 62.1 months (95% CI 18.1–unknown) versus 5.3 months (95% CI 2.8–unknown; P = 0.08) for patients with EBRT and 6.9 months (95% CI 5.0–45.6; P = 0.02) for patients without SBRT. In patients who do not receive systemic therapy, treatment with postoperative SBRT may increase survival time compared with patients not receiving SBRT.