Dosimetric Comparison In3-Dimensional Conformal Radiotherapy (3D-CRT) And Intensity-Modulated Radiotherapy (IMRT) For Thoracic Middle Esophageal Carcinoma

Purpose：The aim of this study was to evaluate the difference of dosimetricresults in target volume and protection of normal important tissuesbetween3D-CRT and IMRT for thoracic middle esophageal carcinoma, andto optimize treatment technique and methods．Materials and Methods: Ten patients with thoracic middle esophagealcarcinoma were involved in this study. The aim of treatment plans was asfollows: prescribed dose of60Gy/30Fx to95%of PTV, V20of lung≤28%,the dose to the spinal cord was within42Gy-43Gy, and no requirement tothe heart. Nine plans were made for each patient, include three3D-CRTplans with3,4,5fields（named3CRT,4CRT and5CRT） and six IMRT planswith3,4,5(include3plans),7fields（named3IMRT,4IMRT,5IMRT1,5IMRT2，5IMRT3and7IMRT）. Evaluation indexes include：mean dose(Dmean)，homogeneity index（HI） and conformity index(CI) of PTV; V5, V10, V20，V30of the left and right lung; V30,V40and Dmeanof heart; Dmaxto the spinalcord． Statistic analysis were performed by SPSS16.0software，95％confidential interval were taken．Results： There were no statistically significant differences of spinalcord Dmax, heart V30，V40and Dmean，L-lung V20and R-lung V15in all plans.Within three3D-CRT plans, no statistically significant differences werefound in Dmean、HI，L-lung V5、V10、V15、V20、V30，R-lung V5、V15、V30. CIand R-lung V10in plan5CRT were lower than plan3CRT and4CRT; R-lungV20in4CRT plan was the lowest one. In5IMRT1plan, L-lung V15,CI werehigher and L-lung V30,R-lung V20, HI, Dmeanwere lower than5CRT plan. CIwas higher,R-lung V20was slightly higher(P=0.05) and Dmean,L-lung V30werelower in4IMRT plan compared to4CRT plan. Compared to3D-CRT plans,3IMRT plans improved CI and reduced L-lung V30.There were no statisticallydifferences of Dmean,HI，L-lung and R-lung V5，V10，V15，V20，R-lung V30in plan3IMRT compared to plan3CRT.In5IMRT1plan, Dmean,HI,CI, L-lung andR-lung V5were lower than5IMRT2plan. Compared to5IMRT3, CI was lowerand L-lung V15, R-lung V5were higher in plan5IMRT1. Dmean,CI,L-lung andR-lung V5、V10were lower but L-lung V30was higher in plan5IMRT3thanplan5IMRT2. In plan5IMRT3, HI,Dmean,R-lung V30were lower than plan3IMRT.R-lung V30,Dmean,and HI were lower in plan4IMRT than plan3IMRT.There wereno significant differences of all parameters include Dmean,HI,CI,L-lung andR-lung V5,V10,V15,V20,V30between5IMRT3plan and4IMRT plan. In7IMRT,CI,L-lung and R-lung V5,V10were higher than5IMRT3. There were nostatistically significant differences in Dmean,HI, L-lung and R-lungV15,V20,V30.Conclusions： Take account of dose of PTV and Lung,4-field3D-CRT plan,4-field IMRT plan and5-field IMRT plan with radiation fields meticulouslydesigned for thoracic middle esophageal carcinoma was feasible.