Demystifying CyberKnife Stereotactic Body Radiation Therapy for Interventional Radiologists

Stereotactic body radiation therapy (SBRT) using CyberKnife system is a relatively new radiation therapy that has demonstrated feasibility, safety, and efficacy with a high local control of various extracranial unresectable primary cancer and oligometastasis. It involves accurate delivery of very high dose of radiation to the target or tumor volume with high precision and conformity, while minimizing the radiation exposure of nontargeted tissue. Radiopaque fiducial markers (FMs) implantation in and around the tumors is required to track the selected tumor during CyberKnife SBRT, especially in those organs moving with respiration. They act as internal radiographic landmarks that maintain a fixed relationship within the tumor and with each other. Although their implantation can be technically demanding, it can be performed using various techniques with varying success; however, percutaneous implantation under image guidance by interventional radiologists is the most common method. Close collaboration between interventional radiologists and radiation oncologists with understanding of the technical aspects of CyberKnife SBRT and FMs implantation has important implications for optimal delivery of therapy and direct impact on the interventional radiology practice in selected patients proposed for CyberKnife SBRT.