Stereotactic body radiation therapy in elderly patients with spinal metastases

PURPOSE: Elderly patients with spinal metastases are often considered poor candidates for aggressive local therapy, due in part to medical comorbidity and limited evidence to guide treatment selection. This study evaluated outcomes following spine stereotactic body radiation therapy (SBRT) in this patient population and examined predictors of local failure (LF) and vertebral compression fracture (VCF). METHODS: A prospectively maintained database of consecutive patients aged ≥ 70 years with available imaging who underwent spine SBRT at a quaternary referral center from 2002 to 2024 was analyzed. The median single-fraction dose was 16 Gy (range: 12-18 Gy), and multi-fraction regimens ranged from 18 to 35 Gy in 2-5 fractions. RESULTS: Of 208 metastases in 161 patients (median age: 75 years, range: 70-94 years), 72% had prior conventional radiotherapy and 76% received a single fraction. The 6-, 12-, 24-, and 36-month cumulative incidence rates were 6%, 9%, 9%, and 10% for LF and 4%, 7%, 8%, and 9% for VCF (median follow-up: 9 months, range: 1-132 months). Gross tumor volume > 37 cc (subdistribution hazard ratio [sHR]: 6.27, 95% confidence interval [CI]: 1.48-26.63, P = 0.013) and Spinal Instability Neoplastic Score (SINS, per-point sHR: 1.23, 95% CI: 1.07-1.42, P = 0.005) were independently associated with LF; only SINS was independently associated with VCF (per-point sHR: 1.19, 95% CI: 1.06-1.34, P = 0.003), and 11 of 17 VCFs required cement augmentation or surgery. Age was associated with overall survival (hazard ratio: 1.05 per year, 95% CI: 1.01-1.09, P = 0.018); no statistically significant association was detected with LF or VCF when age was analyzed continuously, at thresholds of 75 or 80 years, or by exploratory maximally selected rank statistical analysis. Complete or partial pain response followed 61 of 148 evaluable treatments (41%) among 186 symptomatic metastases, and 18% of patients had grade 1-2 radiation toxicity. CONCLUSION: Spine SBRT, predominantly single-fraction reirradiation, was associated with low rates of LF and VCF; chronologic age alone should not preclude its use in appropriately selected elderly patients.