Delineating neck targets for intensity- modulated radiation therapy of head and neck cancer. What we learned from marginal recurrences?

Delineation of the targets for intensity-modulated radiation therapy (IMRT) of the head and neck is a crucial step in treatment planning, determining the risks of marginal or out-of-field local/regional recurrences. Delineation of the gross tumor volumes needs to take into account both radiological (CT, MRI, PET) and clinical findings, discussed in this paper. In contrast, the delineation of the clinical target volumes depends solely on the physician's judgement and knowledge of the natural history and spread pattern of head and neck cancer. While much of this information exists in older literature, new information has been gained from the pattern of recurrences observed after IMRT of head and neck cancer. This review concentrates on this information and on the lessons gained from these recurrences at our institution.