The objective of this study was to compare clinical outcomes following single fraction versus fractionated stereotactic body radiotherapy (SBRT) for spinal metastases.
Materials and Methods:
A multi-institutional registry was queried for patients with spinal metastases treated with single-fraction or fractionated SBRT. Potential predictive factors of local control (LC) and overall survival were evaluated. Pretreatment and posttreatment Visual Analog Scale scores were analyzed to examine initial and durable pain responses and complete response (CR) rates. Logistic regression was utilized to assess potential correlations between pain response, biologically effective dose (BED), and fractionation.
Four hundred sixty-six patients with 514 lesions treated with SBRT were identified; 209 and 104 lesions had information on LC and pain, respectively. The median pain score of patients with symptoms was 6 (range: 3 to 10). The median follow-up was 8.9 months (range: 0.4 to 125.5 mo). Utilizing Karnofsky Performance Score, age, and primary site (lung and/or nonbreast), 1-year overall survival rates were 76.1%, 59.1%, 54.9%, 37.2%, and 23.5% for patients with 0 to 4 of these factors, respectively (P<0.0001). One- and 2-year LC rates were 79.9% and 73.6%, respectively. Eighty-six patients (82.7%) had an initial pain response with a median decline of 3.5 and a CR rate of 47.1%. Sixty-five patients (62.5%) had a durable pain response with a median decline of 2 and a CR rate of 20.2%. Higher initial CR rates were observed with BED10 ≥51 Gy10 (58.7% vs. 37.9%; P=0.04).
Following SBRT, encouraging palliative responses with >80% and 60% of patients having initial and durable pain responses, respectively. Dose escalation may result in improved initial CR rates. Performance status, age, and primary histology are factors to consider in the absence of pain.