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-field 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.