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Background: This study was aimed at developing and validating a decision‐making tool predictive of overall survival (OS) for patients receiving stereotactic body radiation therapy (SBRT) for spinal metastases. Methods: Three hundred sixty‐one patients at one institution were used for the training set, and 182 at a second institution were used for external validation. Treatments most commonly involved one or three fractions of spine SBRT. Exclusion criteria included proton therapy and benign histologies. Results: The final model consisted of the following variables and scores: Spinal Instability Neoplastic Score (SINS) ≥ 6 (1), time from primary diagnosis < 21 months (1), Eastern Cooperative Oncology Group (ECOG) performance status = 1 (1) or ECOG performance status > 1 (2), and >1 organ system involved (1). Each variable was an independent predictor of OS (p <.001), and each 1‐point increase in the score was associated with a hazard ratio of 2.01 (95% confidence interval [CI], 1.79–2.25; p <.0001). The concordance value was 0.75 (95% CI, 0.71–0.78). The scores were discretized into three groups—favorable (score = 0–1), intermediate (score = 2), and poor survival (score = 3–5)—with 2‐year OS rates of 84% (95% CI, 79%–90%), 46% (95% CI, 36%–59%), and 21% (95% CI, 14%–32%), respectively (p <.0001 for each). In the external validation set (182 patients), the score was also predictive of OS (p <.0001). Increasing SINS was predictive of decreased OS as a continuous variable (p <.0001). Conclusions: This novel score is proposed as a decision‐making tool to help to optimize patient selection for spine SBRT. SINS may be an independent predictor of OS. A model predictive of overall survival after spine stereotactic body radiation therapy (SBRT) has been developed and externally validated, and it provides a decision‐making tool to help to optimize patient selection for spine SBRT. The model components are the Spinal Instability Neoplastic Score, the time from diagnosis, the performance status, and the organ systems involved. [ABSTRACT FROM AUTHOR]

• We report a large institutional experience of over 500 spine SBRT treatment with robust follow-up, demonstrating favorable local control and overall survival. • We demonstrate the efficacy and safety of dose escalation via simultaneous integrated boost within the setting of primarily single fraction spine SBRT. • We identify a clinically meaningful dose threshold of 14–15.3 Gy minimum dose to the GTV, which, when achieved, is associated with a statistically significant reduction in local failure. This provides an actionable recommendation and target for spine SBRT treatment planning. • We confirm the relevance of epidural and soft tissue involvement as clinical factors associated with an increased risk of local failure after spine SBRT. Metastasis-directed stereotactic body radiation therapy (SBRT) has demonstrated robust clinical benefits in carefully selected patients, improving local control and even overall survival (OS). We assess a large database to determine clinical and dosimetric predictors of local failure after spine SBRT. Spine SBRT treatments with imaging follow-up were identified. Patients were treated with a simultaneous integrated boost technique using 1 or 3 fractions, delivering 20–24 Gy in 1 fraction to the gross tumor volume (GTV) and 16 Gy to the low dose volume (or 27–36 Gy and 21–24 Gy for 3 fraction treatments). Exclusions included: lack of imaging follow-up, proton therapy, and benign primary histologies. 522 eligible spine SBRT treatments (68 % single fraction) were identified in 377 unique patients. Patients had a median OS of 43.7 months (95 % confidence interval: 34.3–54.4). The cumulative incidence of local failure was 10.5 % (7.4–13.4) at 1 year and 16.3 % (12.6–19.9) at 2 years. Local control was maximized at 15.3 Gy minimum dose for single-fraction treatment (HR = 0.31, 95 % CI: 0.17 – 0.56, p < 0.0001) and confirmed via multivariable analyses. Cumulative incidence of local failure was 6.1 % (2.6–9.4) vs. 14.2 % (8.3–19.8) at 1 year using this cut-off, with comparable findings for minimum 14 Gy. Additionally, epidural and soft tissue involvement were predictive of local failure (HR = 1.77 and 2.30). Spine SBRT offers favorable local control; however, minimum dose to the GTV has a strong association with local control. Achieving GTV minimum dose of 14–15.3 Gy with single fraction SBRT is recommended whenever possible. [ABSTRACT FROM AUTHOR]