Changes in Spinal Instability After Combined Therapy of Conventional Radiotherapy and Bone Modifying Agents for Painful Vertebral Bone Metastases

Abstract

Precise assessment of spinal instability is critical at the beginning and after radiotherapy for selection of the treatment and evaluating the effectiveness of radiotherapy. We investigated changes of spinal instability after radiotherapy and examined potential risk factors for the difference of the outcome of spinal instability for painful spinal metastases. We evaluated 81 patients who received radiotherapy for painful vertebral metastases in our institution between 2012 and 2016. The pain at the vertebrae was assessed. Radiological responses of irradiated vertebrae were assessed by computed tomography. Spinal instability was assessed by Spinal Instability Neoplastic Score (SINS). Follow-up assessments were done at the start of radiotherapy and at 1, 2, 3, 4, and 6 months after radiotherapy. At each of one to six months, pain disappeared in 62%, 84%, 93%, 98%, and 100% of patients. The median SINS were 8, 7, 6, 5, 5, and 4 at the beginning of radiotherapy and after 1, 2, 3, 4, and 6 months, respectively, which significantly decreased over time (P < 0.001). Multivariate analysis revealed that PLISE was the only risk factor for spinal instability at one month. In conclusion, spinal instability significantly improved over time after radiotherapy. Clinicians should take attention to PLISE in the radiotherapy of vertebral metastases.