早期鼻咽癌三维适形、常规和传统外照射计划的剂量学评价

传统鼻咽癌外照射技术存在不少的缺陷,改进鼻咽癌外照射技术已成为提高鼻咽癌疗效的一个努力方向,本研究利用三维治疗计划系统对鼻咽癌传统、常规和三维适形放疗(3D CRT)计划作剂量学比较,评估采用不同方法的意义。

Dosimetric evaluation for three dimensional conformal, conventional, and traditional radiotherapy plans for patients with early nasopharyngeal carcinoma

BACKGROUND &OBJECTIVE:Traditional external beam irradiation techniques for nasopharyngeal carcinoma have a lot of shortcomings, and improving external beam techniques have become an endeavor to enhance curative effectiveness. This study was designed to compare the dose distribution of three dimensional conformal radiotherapy (3D CRT) with traditional and conventional radiotherapy plans in the patients with early nasopharyngeal carcinoma using three dimensional treatment planning system. METHODS: Twenty two patients with early nasopharyngeal carcinoma were selected. Traditional, conventional, and 3D CRT plans were made for each of them and compared with respect to target coverage (V95), normal tissue sparing (D50, D33, and D5, etc), normal tissue complication probability (NTCP). RESULTS: Dosimetric comparison indicated that the V95 of PTVnx60 and PTVnx50 for three different plans were 90.29%and 77.67%(traditional), 98.44%and 98.85%(conventional), 99.98%and 99.63%(3D CRT), respectively; and both conventional and 3D CRT had satisfied dose coverage of target volume especially in subclinical lesion region compared with traditional radiotherapy. With respect to normal tissue sparing, 3D CRT and conventional treatment plans could spare more brainstem, temporal lobe, optic chiasm, and pituitary than traditional plans; and 3D CRT could spare more parotid gland and temporomandibular joint than traditional and conventional treatments. CONCLUSION: Considering the dose distribution of the three treatment plans, both conventional and 3D CRT had satisfied dose coverage of target volume especially in subclinical lesion region compared with traditional radiotherapy, and 3D CRT plans can spare more normal tissues such as parotid gland and temporomandibular joint etc, and decrease their NTCP while it get the same dose distribution in target volume as traditional and conventional plans do in the treatment of early nasopharyngeal carcinoma.