Current status and problems of IMRT for head and neck cancers

There are some OARs (organs at risk), such as the retina, optic nerves, optic chiasm, spinal cord, cochlea, and parotid glands in head and neck tumors. Usually the target is not geometrically well separated from OARs, and adding intensity modulation of the beam may be the only way to adequately treat the target while limiting the dose to surrounding OARs. Intensity-modulated radiation therapy (IMRT) enables us to deliver higher dose to the target while maintaining a low dose to OARs. It appears that patients treated with IMRT recover their salivary flow faster and more completely than those treated with conventional radiotherapy. IMRT is a good indication for nasopharyngeal cancer, oropharyngeal cancer, paranasal sinus cancer, and cervical esophageal cancer. Usually, the dose distribution is quite inhomogeneous within the field from the high neck to upper mediastinum using the conventional radiotherapy technique. On the other hand, we can deliver a homogeneous dose distribution to this region with IMRT. IMRT is an effective treatment method for head and neck tumors. (author)