Impact of recent clinical trials on meta-analysis of stereotactic body radiation therapy for spine metastases and urgent call for consistent study endpoints

Pain from spinal metastases can result in significant impact to patients' quality of life. Conventional external beam radiation therapy (cEBRT) has long been shown to be effective in the pain control of patients with spinal metastases. With the advancement in radiation therapy, stereotactic body radiation therapy (SBRT) has been increasingly adopted for the treatment of spinal metastases. Multiple randomised controlled trials (RCT) have been performed to evaluate whether SBRT provides better pain relief compared to cEBRT. Previous meta-analyses showed that SBRT have significantly better complete pain response at 3 months compared to cEBRT. This report updates meta-analyses by incorporating the complete pain response data obtained from personal communication with the NRG Oncology Radiation Therapy Oncology Group (RTOG) 0631 principal investigator and the recently published RCT by Guckenberger et al. The results demonstrate that the results for complete pain response at 3 months have now changed and no longer favour SBRT. It is postulated that inconsistent definitions and reporting of study endpoints, specifically regarding vertebral compression fractures induced by radiation therapy, could be possible reasons for the difference in meta-analyses results. A consensus for standardizing study endpoints for future clinical trials in SBRT for painful bone metastases is needed to allow for better interpretation of study results.