Research On The Target Area Changes During Intensity-modulated Radiation Therapy For Esophageal Cancer

Purpose:Objective To compare the volume and position (center) ofesophageal cancer target area during the intensity modulated radiationtherapy for esophageal cancer, as well as the changes in the target areaand the dose of normal tissues based on the original physical plan, toanalyze the law of changes in target area and dose distribution, andto explore the most appropriate time and solution for the adjustmentof treatment plan.Materials and methods:Fourteen cases of esophageal cancer patients wereselected for radical intensity-modulated radiation therapy, with theplan design requirements of95%PTV60-66GY/30-33F, both left and rightlung V20<28%, spinal cord dose Dmax<45GY, heart dose V40≤40%. One groupof images (named as1p, similarly hereinafter) were collected for eachpatient before treatment,2groups of images were collected duringtreatment (collect once per10times of treatment, named as2p and3p),and one group of images were collected at the end of treatment (namedas4p); In this way, besides the positioning CT image, the patient hada total of4groups of3D CT images.The tumor observation indicatorsand the dose distribution was calculated for each patient on theoriginally planned4groups of images. The tumor observation indicatorsinclude the volume and location (center) of PTV; Dose observationindicators include Dmean, HI and CI of PTV; Both left and right lungs V5and V20; Dmaxand V45of the spinal cord; V40of the heart. Use the SPSS18.0statistical software for the repeated measures design analysis ofvariance at the credibility interval of95%, to obtain the significancelevel of0.05.Results By comparison of esophageal cancer target area on4groups of CT images between different irradiation time, the volume of PTV hasstatistical difference, but the position (center) has no statisticaldifference; The dose distribution between different irradiation time,V5and V20of all-lung have no statistical difference, Dmaxand V45of thespinal cord have no statistical difference, and V40of the heart has nostatistical difference; Dmean, HI and CI of PTV have statistical difference.From pairwise comparison of CT images between different irradiation time,for the volume of PTV:1p has obvious difference from2p,3p and4p,where1p has statistical difference from2p,2p has statistical differencefrom3p, and3p has no statistical difference from4p; From pairwisecomparison of dose distribution of CT images, for the Dmeanof PTV:1phas obvious difference from2p,3p and4p, where1p has statisticaldifference from2p,2p has no statistical difference from3p, and3phas no statistical difference from4p; For the HI of PTV:1p has obviousdifference from2p,3p and4p, where1p has statistical difference from2p,2p has no statistical difference from3p, and3p has no statisticaldifference4p; For the CI of PTV:1p has obvious difference from2p,3p and4p, where1p has statistical difference from2p,2p has statisticaldifference from3p, and3p has statistical difference4p.Conclusions: By the comprehensive consideration of planned target areaand lung dose, during the intensity-modulated radiation therapy forradical cure of esophageal cancer, it is preferred to collect again theimages of target area in time of the20th treatment for the adjustmentof the plan.