Comparison Of Thyroid Gland Doses Associated With Three-dimensional Conformal Radiotherapy Versus Intensity-modulated Radiotherapy For Cervical Esophageal Cancer

To compare thyroid gland radiation exposure using intensity-modulated radiotherapy (IMRT) vs. three-dimentional conformal radiotherapy (3D-CRT) treatment plans for patients with cervical esophageal cancer undergoing chemoradiation.Methods and Materials:Sixty-five patients with cervical esophageal cancer were created treatment planning with IMRT and 3D-CRT respectively from March 2013 to June 2015 were identified. All plannings were created with 60.0Gy. Dose-Volume histograms of the planning target volume, spinal cord,and other critical normal tissues were compared between the IMRT and 3D-CRT plans, and selected parameters were statistically evaluated using the Wilcoxon rank-sum test.Results:Intensity-modulated radiotherapy planning showed significant reduction (P< 0.05) in thyroid gland over 3D-CRT plans as assessed by V45(35%vs.83%).There are also significant sparing of the spinal cord (average mean does,39.0Gy vs.43.OGy).There was no significant difference in percentage of total lung volume receiving at least V5,V20,V30Gy or in the mean lung dose between the planning methods. Intensity-modulated radiotherapy achieved a signifcant improvement in target Conformality Index,CI=Vt,ref/Vt.Vt,ref/Vref.CI60Gyl.1(IMRT)Vs.1.8(3D-CRT).Ho mogeneityindex(HI),HI=Dmax-Dmin/Dmean.A 7-beam IMRT technique was found to be superior to 3D-CRT with respect to dose conformal and homogeneity index.Conclusion:Treatment of patiens with cervical esophageal cancer using IMRT significantly decreased the exposure of the thyroid gland and spinal cord when compared with 3D-CRT.Long-term studies are necessary to determine how this will impact on development of thyroid gland.