Skin surface markers for stereotactic body radiation therapy of sternal metastasis.

Stereotactic body radiation therapy is an effective and safe treatment modality for bone metastasis which allows clinicians to accurately target lesions to high doses while minimizing dose to organs at risk. The commercially available CyberKnife® Xsight™ Spine Tracking System (Accuray, Inc., Sunnyvale, CA) tracks static skeletal structures and eliminates the need for implanted fiducial markers (FMs). However, the Xsight™ Spine Tracking system is not appropriate for bone metastases outside the spine, which are moving due to respiration and ,typically, FMs have to be implanted close to the lesion. These FMs will be used to track the dynamic target. For targets close to the surface, non-invasive fixation of the FMs to the patient's skin could be an option.