Application of dose heterogeneity in the target volume in intensity-modulated radiation therapy of esophageal cancer

Abstract

Objective To investigate the advantage of the intensity-modulated radiotherapy treatment (IMRT) by allowing dose heterogeneity in the target volume in esophageal cancer treatment planning.Methods Two sets of 5-field IMRT planning were designed for 10 esophageal cancer patients upon the condition of appropriate clinical tolerance level with the prescription dose of 60 Gy to 95% of the planned target volume (PTV) and the maximum dose of 45 Gy to the spinal cord:the IMRT with rigid restriction of the maximum homogeneous dose to the PTV within 63 Gy prescribing a homogeneous dose ( IMRThom ) and the IMRT allowing dose heterogeneity by loosening the constraints on maximum dose in the PTV to 69 Gy ( IMRTinhom ).Dosimetric comparison was conducted by using dose-volume histograms.Results Compared to IMRThom, the minimum dose (t = -3.37,P =0.012), maximum dose (t = - 23.58,P = 0.000), mean dose ( t = - 4.95, P = 0.002 ), and heterogeneity index ( t = - 11.06, P =0.000) in PTV of the IMRTinhom were all significantly increased, and the values of V5 (t = 6.96, P =0.000), V10(t=5.24,P=0.001) , V15(t=4.73,P=0.002) , V20(t=8.08,P=0.000) , V25(t=8.58,P = 0.000), and mean dose (t = 7.28,P = 0.000) of the normal lungs were all significantly lower.There were no significant differences in all the indexes for the mean dose to the heart and maximum dose to the spinal cord between these 2 set of planning.Conclusions The IMRT plan allowing dose heterogeneity in the PTV escalates the prescription dose and decreases the doses to the lungs. Key words: Esophageal carcinoma; Radiation therapy; Intensity modulated radiation therapy; Dose heterogeneity; Lung dose