Dosimetric comparison of different schemes for arrange beams in intensity modulated radiation therapy for mid- and distal- esophageal carcinoma

Objective To analyze the difference between five-field plan and seven-field plan in intensity modulated radiation therapy for patients with mid- and distal-esophageal carcinoma,and to find out the optimal beam arrangement.Methods Five-field plan and seven-field plan were designed for each of 12 patients with mid- and distal-esophageal carcinoma.95％ of planning target volume was required to achieve prescription dose.Dose-volume histograms statistics,dose uniformity,and dose conformity in every patient were compared respectively.Results Superior dose conformity for planning target volume was shown in seven-ficld plan (t=2.681,P＜0.05).Difference was not significant between uniformity in seven-field plan and that in five-field plan.Difference was not significant between doses received by organs at risk,such as spinal cord and heart,in seven-field plan and those in five-field plan.V5,V10,V15 of lungs in five-field plan were lower significantly than those in seven-field plan (t=-7.938,-12.055 and -4.859,all P＜0.05).Conclusions For patients with thoracic esophageal carcinoma treated by intensity modulate radiation therapy,compared with 7-fielded plan,the volume of lungs with lower dose could be reduced on the premise of acceptable planning target volume coverage by the application of five-plan.Therefore,radiation-induced lung injury occurrence probability would be reduced,and the patient's quality of life would be improved.Five-field plan would be worth applying in the clinical work. Key words: Esophageal neoplasms;  Radiotherapy planning, computer-assisted;  Radiation therapy,intensity-modulated;  Case-control studies