Implementation of intensity-modulated radiation therapy in head and neck tumors: what are the important data for biological optimization?

Intensity-modulated radiation therapy (IMRT) for head and neck (HN) tumors refers to a new approach to the whole treatment procedure from patient immobilization to beam delivery. Implementation of IMRT thus requires knowledge of setup uncertainties, adequate selection and delineation of target volumes based on optimal imaging modalities, appropriate specification and dose prescription regarding dose-volume constraints, and ad hoc quality control of both the clinical and physical aspects of the whole procedure. A large number of issues still need to be resolved and/or further refined. In particular, data need to be accumulated in a better integration of improved dose distribution into the fractionation strategy, and in-depth knowledge of dose-volume constraints for normal tissues at risk. In this article, these issues will be reviewed and put into the prospective of IMRT treatment.