Radiation-Induced Bone Toxicity

Abstract

Normal bone is commonly irradiated during radiation therapy (RT). The true impact of focal radiation on bone tissue remains unclear. The goal of this paper is to present the current understanding of radiation effects on the bone as it pertains to clinically observed radiation side effects. An increased risk of local fracture has been associated with RT-induced bone loss in the pelvis, vertebrae, and ribs. This bone loss appears to occur early after and/or during treatment, which suggests that reactive remodeling of the bone via osteoclast activity is a primary contributor to bone loss and fractures. Several reports have quantified the structural and histological changes observed after bone irradiation. These include changes in bone density and cortical thickness, as well as alterations in both the number and activity of the cells responsible for bone turnover that arise from hematopoietic and mesenchymal lineages: namely, osteoclasts and osteoblasts. All of these changes likely play an important role in the increased risk of fracture reported with RT. However, more research is needed to fully understand the mechanisms of bone damage and its relationship to modifiable factors such as beam energy, dose, photon or charged particle radiation, linear energy transfer (LET), fractionation, and field size.