| Purpose: To compare the plans of three-dimensional conformal radiotherapy technique (3D-CRT) using for boost with conventional treatment plans for 7 patients of locally advanced nasopharyngeal carcinoma.Methods and Materials: Between 2001 and 2002, 7 patients with advanced nasopharyngeal carcinoma received conventional external beam therapy followed by a 3D-CRT boost, all patients were poorly differentiated squamous cell carcinoma.4 cases with both side parapharyngeal space involving,3 cases with single- parapharyngeal involving, conventional treatment plans and 3D-CRT plans created by Topslane 3D-CRT plan system were compared with respect to dose coverage of the tumor target volume, dose to the sensitive normal tissue structures,dose conformality and dose heterogeneity, base on axial dose distribution figure and dose-volume histogram (DVH).Results: Maximum and minimum planning target volume (PTV) dose increased from 72.71Gy and 69.86 Gy with the traditional plan, to 73.1 and 70.02 Gy with the 3D-CRT plans (p>0. 05). Average maximum cord and brain stem dose decreased from 57.92 Gy and54.65Gy with the traditional plan, to 40.85Gy and 41.33Gy with the 3D plan(p<0. 05). The maximum dose of mandible and temporal lobes and the mean parotid gland dose decreased with 3D-CRT. axial dose distribution and dose-volume histogram (DVH) figures show that 3D-CRT plans achieved better sensitive normal tissue structure sparing, and the planned dose distributions were more conformal to the tumor target volume in the 3D-CRT plans than those in the conventional plans, dose heterogeneity in two plans show no significant defference.Conclusions: Compared to conventional techniques, 3D-CRT techniques provide improved tumor target coverage with significantly better sparing of sensitive normal tissue structures including cord , brain stem, mandible , temporal lobes and parotid gland in the treatment of locally advanced nasopharyngeal carcinoma. Target conformality improved in 3D-CRT plans .
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