الفهرس 
Conventional radiation therapy in head and neckOnly 14 pages are availabe for public view
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Abstract
Cancer of the head and neck region comprises a heterogenous group of neoplasms, which have varying biological behavior and different degrees of radioresponsiveness. They are grouped together because, of their similar etiology, presentation and management. Management of this group of tumors is usually with surgery, radiation therapy, or a combination of both (Emami, et aI, 1996). In national cancer institute m Egypt primary head and neck cancers constitute about’ 17% of all malignant tumors. Higher frequency is reported in India (oral cavity alone is 40°!c» and China (nasopharyngeal cancer is 180/0 (El-Bolkain, 2000). In the united states, primary head and neck cancers constitute about 50/0 of all malignant tumors, more than 42000 new cases diagnosed annually and more than 500,000 cases diagnosed annually world wide (Harari,2003). The complex anatomy of the head and neck region, with its four different major sites and 17 subsites and the intimate proximity Of each to critical Structures such as spinal cord, optic nerve and chiasma, has rendered the treatment planning of this region one of the most difficult challenges for radiation oncologists. Each site has its own. natural history •with specific routes of local extension as well as nodal dissemination. Fundamental knowledge .about the natural behavior of this cancer is essential for delination of the volumes to be irradiated (Lohr, et al, 2000). In routine practice in many centers, the treatment of the head and neck tumors involve two lateral, parallel opposed portals encompassing the primary and nodal areas, with an additional separate low neck portal for treatment of the supra-clavicular nodes when indicated (Vokes, et al, 1993).