Spine Stereotactic Body Radiotherapy Outcomes in Patients with Concurrent Brain Metastases

Objectives: Stereotactic body radiotherapy (SBRT) is an emerging technique for maximizing tumor and pain control in selected patients with spinal metastases. Outcomes for those with concurrent brain metastases (CBM) have not been well-described previously. The goal of this study was to compare outcomes for patients with or without CBM treated with spine SBRT.

Methods: Records of all patients treated with SBRT for spine metastases at our institution from January 2008 to January 2014 were reviewed. Chi-square analyses and the Mann-Whitney test were used to assess the association of CBM (defined as brain metastasis present prior to or at the time of spinal SBRT) with potential covariates. The log-rank test and Cox proportional hazards regression were used to evaluate the impact of CBM on overall survival and local control from the time of the first course of spine SBRT.

Results: Seventy-eight patients and a total of 86 SBRT lesions were treated. Median patient age was 60 years (range: 38-84 years); 28.2% had radioresistant histologies. A single fraction was used in 91.0% of treatments. One-year local control was 89.4%, and one-year overall survival was 45.8%. A total of 19 patients (24.4%) had CBM. Among these CBM patients, 18 (94.7%) underwent intracranial radiosurgery and nine (47.4%) were diagnosed synchronously with their spine metastases. Local control was not significantly different between patients with or without CBM on univariable (median: 58 months vs. not reached, p = 0.53) or multivariable analyses (HR 0.52, 95% CI 0.06-4.33). Overall survival was also not significantly different between patients with or without CBM on univariable (median: 7 vs. 11 months, log-rank p = 0.12) or multivariable analyses (HR 1.62, 95% CI 0.87-3.03).

Conclusions: Patients with CBM do not appear to have a statistically significant detriment in clinical outcomes, suggesting that CBM should not necessarily be considered a contraindication for spine SBRT. Although our study is limited by significant heterogeneity in tumor type within our series, future work should focus on the development of reliable survival prognosticators for patients undergoing spinal radiosurgery. Nearly half of the patients with CBM were diagnosed synchronously with their spine metastases, emphasizing the usefulness of obtaining a brain MRI for complete staging prior to spine SBRT.