Stereotactic body radiotherapy as a primary treatment for spinal metastasis: a single institution experience

Background: To investigate the clinical outcome including efficacy and safety of stereotactic body radiotherapy (SBRT) in management of spinal metastasis. Methods: Between 2010 and 2017, 26 patients with 32 metastatic spine lesions treated with SBRT were retrospectively reviewed. Local control (LC), overall survival (OS), prognostic factors and toxicity were analyzed. Results: There were 15 female and 11 male patients (median age, 62 years; range 27 to 88 years). 32 metastatic spine lesions were treated with SBRT. The most frequent lesions treated were metastatic tumours of the lung (n=19), other primary histologies were prostate (n=4), breast (n=3), sarcoma (n=2), hepatocellular carcinoma (n=1), renal cell carcinoma (n=1), stomach (n=1), nasopharyngeal carcinoma (n=1). Thoracic spine was the most common site treated (n=18), followed by lumbosacral spine (n=12) and cervical spine (n=2). The most common dose fractionation used was 24 Gy in 3Fr. The median EQD2/10 Gy was 36 Gy (range, 34.7-59.7 Gy). The median planning target volume (PTV) was 50 cc (range, 10.4-194 cc). The median follow up was 23.4 months (range, 3-103 months). For the entire cohort, local tumour control (LC) at 1 year and 2 years were 83% and 71% respectively. The median OS was 30.6 months. The OS at 1 year and 2 years were 88% and 59% respectively. On univariate analysis for OS, presence of visceral metastases (HR 11.13, P=0.001), uncontrolled primary disease (HR 4.57, P=0.02) and presence of more than 3 vertebral metastasis (HR 5.50, P=0.04) were corelated with worst outcomes. On multivariate analysis for OS, only presence of visceral metastasis remained significant (HR 23.99, P=0.002). Acute toxicity mainly pain flare occurred in 16% of the treated lesions that can be managed with analgesics and steroid. Other adverse events were rare and no radiation induced myelopathy reported. Conclusions: This study reports SBRT is a safe and effective treatment for spinal metastasis. Prognostic factors were identified to guide patient selection that would benefit from this treatment.