Intensity-modulated radiotherapy for carcinoma of the head and neck.

Intensity-modulated radiotherapy (IMRT) is the next evolutionary step of three-dimensional conformal radiotherapy (3-DCRT). IMRT plans are generated with computer-optimized nonuniform radiation beam intensities incident on a target or patient. The dose distributions in IMRT show significantly higher conformality compared with other methods of external-beam radiation delivery, including conventional 3-DCRT. This significant conformality is advantageous in malignancies of the head and neck, where differential dosage is needed to deliver higher doses to the primary tumor and lower doses to areas of subclinical disease. Topics discussed in this review include target delineation, salivary gland sparing, and treatment of specific primary sites. Available data from the literature are presented, including patterns of failure after IMRT. To illustrate the potential role of IMRT in dose escalation and sparing of normal tissues, fractionation strategies in the definitive treatment of head and neck malignancies are presented. In addition, the role of IMRT in treatment of recurrent malignancies of the head and neck is explored. Finally, general concepts of helical tomotherapy are discussed.