International Consensus on Delineation of Target Volumes and Organs at Risk

Abstract Accurate delineation of target volumes and organs-at-risk (OAR) is important in the era of intensity-modulated radiotherapy where the dose distribution is highly conformal, yet significant variations in practice exist. Establishing international guidelines and consensus based on basic knowledge of disease behavior and clinical data can enhance global consistency and help to identify controversies. In the process of radiotherapy planning, a fine balance between dose-to-target volumes and constraints to the OAR should be attained in order to maximize the risk-to-benefit ratio. Integrating the most optimal radiotherapy fractionation and schedule is also critical in modulating radiobiological response. This chapter will give an overview of these essential concepts in radiotherapy planning and review the latest data and recommendations.