Dosimetric Evaluation of Three Dimensional Conformal and Conventional Treatment Plans of Early Untreated Carcinoma of Nasopharynx

Objective： Conventional external beam irradiation techniques for nasopharyngeal carcinoma have limitations, and improving external beam irradiation techniques is needed to enhance the curative rate. This study was designed to cvaluate the difference in dose distribution of three dimensional conformal radiotherapy （3D CRT） and conventional treatment plan in early untreated nasopharyngeal carcinoma using a three dimensional treatment planning system. Methods： Twenty-two patients with early untreated nasopharyngeal carcinoma were selected. Conventional and 3D CRT plans were made for each of them and compared with respect to target volume coverage （V95）,normal tissue sparing （D50, D33 and D5, etc）, normal tissue complication probability （NTCP）. Results： The average volumetric dose comparison indicated that the V95 of PTVnx70 were 98.22% and 99.99% （P=0.06）, and PTVnd60, 98.41% and 99.63% （P=1.00）, PTV,x60, 98.44% and 99.98% （P=0.03）, PTVnx50, 98.85% and 99.63% （P=0.02） in conventional and 3DCRT treatment plans respectively. With respect to normal tissue sparing, the average D50 of unilateral parotid glands were 51.91 Gy and 64.30 Gy （P=0.00） respectively, and the unilateral temporomandibular joints, 49.98 Gy and 64.47 Gy （P=0.00）, the Dlcc of spinal cords, 44.98 Gy and 48.09 Gy （P=0.00） in 3D CRT and conventional plans. Conclusion： Though only a little bit better dose coverage of target volume in subclinical lesion region was reached in 3D CRT plans, it spared more normal tissues e.g. parotid glands and temporomandibular joints etc and decreased their NTCP while it got the similar dose distribution in target volumes as conventional plans did for these early nasopharyngeal carcinoma cases.

Neck dissection for recurrent and persistent lymph nodes of nasopharyngeal carcinoma after radiotherapy： effect and choice

Objective： To investigate the best surgical mode for the patients of nasopharyngeal carcinoma with recurrent and persistent lymph nodes after radiotherapy. Methods： The clinical data of 88 patients of nasopharyngeal carcinoma with recurrent and persistent lymph nodes after radiotherapy were analyzed retrospectively. The levels of involved lymph nodes and the relationship among the levels were analyzed; the survival rate and recurrent rate of the surgical modes including radical neck dissection （RND）, modified radical neck dissection （MRND）, selective neck dissection （SND）, and lymph node resection （LNR） were analyzed; the role of postoperative radiotherapy was evaluated. Results： （1） The recurrent and persistent lymph nodes mainly located in level Ⅱ（55.6% and 58.6%, respectively）, next was level Ⅲ and rarely in level Ⅳ, Ⅴ, and Ⅰ, but the number of levels Ⅳ Ⅴ, and Ⅰ with cancer-bearing lymph nodes was relatively more than that of clinical measurement. （2） Patients with lymph nodes involved in level Ⅲ and Ⅳ, usually, have other levels involved simultaneously; the percentages were 63.6% and 88.9%, respectively. However, the lymph nodes in level Ⅱ and Ⅴ were mainly isolated. （3） The 5-year survival rate and recurrent rate of the whole group were 42.77% and 22.7%, respectively. （4） The 5-year survival rates of RND, MRND, SND, and LMR groups were 39.75%, 60.00%, 37.87%, and 44.10%, respectively; the differences were insignificant （Log-rank = 1.0, P = 0.8011）; the recurrent rate between the extensive and local surgery groups were insignificant （X^2 = 0.470, P = 0.493）. （5） The 5-year survival rates of the patients with and without postoperative radiotherapy were 39.06% and 45.26%, respectively; the difference was insignificant （Log-rank = 0.06, P = 0.8138）. Conclusion： The extensive surgery was recommended when the recurrent and persistent lymph nodes were more than one level involved or very large or immovable, otherwise, the SND should be performed and postoperative radiotherapy was important compensation if necessary.