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

Abstract

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 or not patients received systemic therapy. Survival analysis was conducted using propensity score matching. Bivariate analysis in the non-systemic therapy group revealed longer survival with SBRT compared to 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 SBRT patients was 22.7 months (95% CI: 12.1 - 52.3) versus 16.1 months (95% CI: 12.7 - 44.0; p = 0.28) for EBRT patients and 16.1 months (95% CI: 12.2 - 21.9; p = 0.07) for non-SBRT patients. Within patients who did not receive systemic therapy, overall median survival for SBRT patients was 62.1 months (95% CI: 18.1 - unknown) versus 5.3 months (95% CI: 2.8 - unknown; p = 0.08) for EBRT patients and 6.9 months (95% CI: 5.0 - 45.6; p = 0.02) for non-SBRT patients. In patients who do not receive systemic therapy, treatment with postoperative SBRT may increase survival time compared to patients not receiving SBRT.