| Objective: To investigate the superiority of the dose distribution and the clinical value of three-dimensional radiation therapy (3DCRT) for the boost treatment of primary nasopharyngeal carcinoma (NPC) or the salvage treatment of locally recurrent NPC.Methods: From June 2001 to December 2002,15 NPC patients treated with 3DCRT.8 primary NPC patients with locally advanced disease used for the boost treatment with a dose of 10-40Gy,the overall dose was 70-76Gy/35-38F /7-7.6weeks; 7 patients with locally recurrent NPC used for the salvage treatment,the dose was 56-66Gy/28-33F/5.6-6.6weeks. According to CT and MRI images to delineate the target ,the gross tumor volume(GTV) was enlarged 5-10mm circumferentialy to form the planning target volume (PTV).5 static conformal portals were delivered with coplanar or non-coplanar irradiation technique.Results: The plans of 3DCRT were compared with the conventional plans in respect to dose conformalilty,dose-volume histogram(DVH) and dose to the organs at risk.90% iso-dose curve was more suitable to the target in 3DCRT,iso-dose curves outside the target decreased steeply. In the area ofparotid glands,pituitary gland and optic chiasma,the dose received decreased significantly.In the high dose area,the dose to the brain also decreased. Without inverse planning and intensity-modulated radiation therapy (IMRT), 3DCRT had no advantage in protecting brain stem and spinal cord. MRI was superior to CT in differentiating the lesions of skull base.All patients had good tolerance,the acute oral side effect was slight.The short-term effectiveness was 100% and 86% respectively.In the 5-21 months' follow-up period,there was no regional failure.Conclusion: 3DCRT is effective and feasible to the treatment of NPC,with good responses and no serious side effect.The long-term survival and possible specific side effect,however, need further investigation.MRI is helpful to delineate tumor volume and find tumor recurrence.
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