Balancing risk and reward in target delineation for highly conformal radiotherapy in head and neck cancer.

The therapeutic index of highly conformal radiotherapy (RT) depends on adequate selection and delineation of the gross tumor volumes, the clinical target volumes, and the tissues and organs whose sparing is likely to gain clinical benefit. Decisions about target and tissue selection and delineation affect the balance of reward and the risk of highly conformal RT. Some of these issues relating to head and neck cancer, including target delineation after tumor shrinkage by induction chemotherapy or at midradiotherapy, are discussed in this article.