Comparison of Clinical Outcomes Stratified by Target Delineation for Patients Undergoing Stereotactic Body Radiotherapy for Spinal Metastases

Abstract

Objective: Stereotactic body radiotherapy (SBRT) is an effective treatment of spinal metastases in the vertebral body. However, variation has existed between practitioners regarding the appropriate target delineation. As such, we compared the tumor control, rates of compression fractures, and pain control for patients who had undergone SBRT for spinal metastases to either the lesion only (LO) or the full vertebral body (FVB).

Methods: A total of 126 spinal metastases in 84 patients had received single-fraction SBRT from January 2009 to February 2015. Of the 126 lesions, 36 (29%) were in the FVB group and 90 were in the LO group. The SBRT plans were reviewed to determine the treatment volume. Odds ratios were used to compare the rates of compression fracture and local failure. Regression analysis was performed to identify the predictors of outcome.

Results: A total of 5 failures had occurred in the FVB group and 14 in the LO group; however, the difference was not statistically significant (P = 0.5). No difference was found in pain reduction between the 2 groups (P = 0.9). Seven post-treatment compression fractures occurred in the LO group and four in the FVB group; however, the difference was not statistically significant (P = 0.6). The minimum dose to the planning target volume, patient age, and planning target volume size were the only significant factors predicting for local failure, vertebral body fracture, and pain control, respectively.

Conclusions: Given that we found no difference in tumor control, pain reduction, or fracture rate between patients treated to the FVB versus the. LO, it might be reasonable to consider SBRT to the LO for select patients.

Keywords: Radiation target delineation; Radiosurgery; Spine metastases; Stereotactic body radiotherapy.