Vertebral body collapse after radiotherapy for spinal metastases

Spinal metastases are common in patients with advanced stages of cancer and frequently cause vertebral body collapse (VBC). Although conventional radiotherapy (RT) is used for spinal metastases, the rates of occurrence of new VBC and progression of VBC at RT initiation have not been fully investigated. The present retrospective study assessed VBC and its associated risk factors after RT over time and evaluated new VBC and progression of VBC in patients who presented with VBC at RT initiation. The study evaluated 177 patients who received RT for vertebral metastases without paralysis between July 2012 and November 2016. Radiological responses of the irradiated vertebrae were assessed using computed tomography. Follow-up assessments were performed at RT initiation and 1, 2, 3, 4 and 6 months after RT. New VBC occurred in 12% of patients with no prior VBC within 1 month of RT. Multivariate analysis revealed that numeric rating scale (NRS) score (≥4) [relative risk (RR), 27.1; 95% confidence interval (CI), 1.86 to 394.9; P=0.016] was associated with the occurrence of new VBC at the 1 month follow-up time point. VBC progression occurred in 51% of the patients with collapse at RT initiation. Multivariate analysis revealed that bone quality (lytic metastases) (RR, 3.1; 95% CI, 1.28 to 7.70; P=0.013), NRS score (≥4) (RR, 3.0; 95% CI, 1.18 to 7.45; P=0.021) and tumor involvement of posterolateral elements of the spine (RR, 2.7; 95% CI, 1.03 to 7.29; P=0.04) were associated with the progression of VBC at the 1 month follow-up time point. The current study findings suggested that clinicians should pay attention to the factors that predict the occurrence of new VBC and VBC progression to ensure proper evaluation of conservative treatment effectiveness and facilitate the determination of patients who need close monitoring.