[Recommendations for the definition of target volumes on computerized dosimetry in oropharyngeal cancers]

The oropharynx includes the base of tongue, tonsil pillars, soft palate, lateral and posterior wall of the hypopharynx. Tumors involving each part of these areas are often treated by external beam radiation therapy. The development of conformal approaches and the implementation of intensity modulated radiation therapy, combined with accurate definition of target volumes, endorsed by the international community, allows to propose guidelines for definition of target volumes. First of all imaging acquisition for dosimetry is reminded. For tumors involving the base of tongue and vallecula, early superficial tumors should be distinguished from tumors involving the muscles, indicating an increased margin defining the clinical target volume around the tumor to 1.5 cm. Tumors developed in the posterior wall of the hypopharynx should include constrictor muscles of the pharynx inside of the CTV. Tonsil carcinomas should be treated with a 1.5 cm margin around the tumor in the three dimensions. In spite of modern imaging, external beam treatment of tumors developed in the soft palate and in palatine arch remains difficult. The high rate of nodal involvement of these tumors and significant rates of bilateral extension have to be taken into consideration. Accurate criteria have been available to integrate a probability of bilateral extension in oropharyngeal tumors. It should be analyzed according to the size of the tumor and the rate of extension in the base of the tongue and in the palatine arch.