Association of radiotherapy with thoracic vertebral fractures in esophageal squamous cell carcinoma: A retrospective cohort study.

To investigate the association between radiotherapy (RT) and thoracic vertebral fractures in esophageal squamous cell carcinoma (ESCC) and explore the risk factors of thoracic vertebral fracture in ESCC who underwent RT. This retrospective cohort study including 602 consecutive ESCC patients examined the association between RT and thoracic vertebral fractures using multivariable Cox proportional hazard models and relevant risk factors of thoracic vertebral fractures based on clinical and RT parameters in patients with ESCC. Followed for a median follow-up of 24 months, 54 patients had thoracic vertebral fractures. The multivariable analysis revealed RT as an independent risk factor after adjusting for clinical risk factors. Univariable analyses associated a 5-Gy increase in vertebral dose to single vertebrae and a 1-time increase in RT fraction with higher risk of vertebral fracture. Adding RT factors (vertebral dose and fraction) and mean vertebral hounsfield unit to the Cox models containing conventional clinical risk factors significantly improved the χ2 value for predicting vertebral fractures (all P < .001). This study revealed RT, as well as increased vertebral dose and RT fractions, as a significant, consistent, and strong vertebral fracture predictor in ESCC. Combined vertebral dose, RT fractions, and vertebral hounsfield unit provided optimal risk stratification for ESCC patients.