The Clinical Research On The Second Scan Of IMRT For Locally Advanced Nasopharyngeal Carcinoma

Purpose:Studies in advantages of the second scan of IMRT for locally advanced nasopharyngeal carcinoma in protection of normal tissues, increase the target dose and short-term efficacy.Experimental method:1.In contrast to the volume of BODY,GTVnx,GTVnd,PGTVnx, PGTVnd,PTV1, and the shortest distance of the spinal cord-GTVnd, the spinal cord-GTVnx, the brainstem-GTVnx and the bilateral lens-GTVnx in the first scan and the second scan of the experiment cases.contrast to the volume of GTVnx、GTVnd、PGTVnx、PGTVnd、PTV1between the first scan of experimental group cases and comparative group cases,in order to explore the difference in target volume of the two groups.The target area of experimental groups and comparative groups were confirmed by the same imaging department professor and the same oncology professor2. Collecting dose distribution of spinal cord,brainstem,bilateral crystal and PGTVnx,PGTVnd,PTV1after continue radiotherapying to experimental group using second scan plan,and PGTVnx224cGy/f, PGTVnd212cGy/f、PTV1185cGy/f were used as its corresponding theoretical dose, obtains the relative volume numerical of relative V100%、V110、V95%、V93%of PGTVnx、PGTVnd、PTV1. Collecting the above index numerical if the first plan was uesd, Analysis high-risk organs and target area of the dose distribution between the first and the second scan. 3.Seeking the diffrences of spinal cord, brainstem, bilateral crystal and PGTVnx, PGTVnd,PTV1average doses between experimental group patients and comparative group patients.4. Reviewing nasopharynx and neck MRI at the end of radiotherapy for3-6months evaluating the recent curative effect.Results:1.Corresponding volume of the BODY,GTVnx,GTVnd,PGTVnx, PGTVnd,PTV1,the shortest distance of the spinal cord-GTVnd,the shortest distance of the brainstem-GTVnx and the shortest distance of the bilateral lens-GTVnx in the first and the second scan were checked by Wilcoxon signed rank test,results are P<0.05, the difference was statistically significant, the shortest distance of spinal cord-GTVnx and the difference of volume in comparative groups PGTVnx, PGTVnd, PTV1with no statistically significant.2.Contrasted dose of brainstem, spinal cord and bilateral lens of the second scan radiotherapy planning and average doses of PGTVnx, PGTVnd,PTV1,and corresponding dose of one-time radiotherapy plan, results were that except for right lens and spinal cord, the does threaten organ of the second scan were lower than those in the first scan,and the dose to the target area were higher than those in the first scan, but only the dose differences of left lens were statistically significant,in the comparison of V100%、V110%、V95%、V93%of PGTVnx、PGTVnd、 PTV1in two groups,the volume of PGTVnd V100%in the second scan was larger than those in the first scan, P<0.05.The rest of the two scan of the program had no significant difference.3.Compared between average dose of spinal cord,brain stem,and crystal and PGTVnx,PGTVnd,PTV1in two groups cases, results were that except for left lens and PGTVnx,the does threaten organ of experimental group were lower than those in comparative groups,and the dose to the target area were higher than those in comparative groups.and the dose of PTV1were higher than those in comparative group significantly, P<0.05.4.The CR rate of experimental groups was41.38%,and the CR rate of comparative groups was31.03%.CR ratio increased by11.35%.Experimental conclusion:Tt is necessary to do the second scan for locally advanced nasophar-yngeal carcinoma with largerly tumor,in order to formulate radiotherapy plans to increase the dose to the target area,protecte organ from harming, and improve the rate of CR of patients.