Dosimetric Comparison Study On Coplanar And Non-coplanar Intensity-Modulated Radiation Therapy Planning For Esophageal Carcinoma

Objective： To select reasonable treatment methods for esophagealcarcinoma,the does distribution by three-dimensional treatment planningsystem (TPS) for target area and normal tissue around esophageal carcinomain coplanar intensity modulated radiation therapy plan and two non-coplanarintensity modulated radiation therapy plans were assessed.Methods: Forty-five patients with untreated esophageal carcinoma wereselected, of which15were of cervical and upper thoracic type, and30were ofmiddle section and lower thoracic section. The Gross tumor volume(GTV),clinical target volume(CTV) and organs at risk were outlined throughCMS-XiO4.4treatment planning system.Three treatment plans were designedfor each patient: plan A, optimized coplanar intensity modulated radiationtherapy plan. plan B and plan C,non-coplanar intensity modulated radiationtherapy plan. The same physical objective function was applied for the samepatient in three plans. The does distribution of the target area and surroundingnormal tissue were evaluated in the three plans in terms of dose-volumehistograma (DVH).Results：(1) Patients with middle section and under thoracic section ofesophageal carcinoma,The Conformity Index(CI) was0.69±0.13,0.41±0.13and0.68±0.15for plan A, plan B and plan C,respectively. The ConformityIndex(CI) of plan B was the lowest, is significantly different from that of planA and plan B.The V5, V10, V20, V30,mean dose of total lung of plan B and Cwere both significantly lower than that from plan A. The V30, V40, V45, V50, V55,mean dose of heart of plan B and V30, V40, V45of heart of plan C were bothsignificantly higher contrast to plan A, but were still within the range ofclinically acceptance. compared with plan A, the D1ccof spinal cord from plan B was significant increased, while, there was no significant difference betweenplan A and C. There was no significant difference among plan A, plan B andplan C in maximal dose, minimus dose, mean dose of PTV,HeterogeneityIndex (HI).(2) patients with cervical and upper thoracic of esophagealcarcinoma, there is no significance among plan A, plan B and plan C inmaximal dose, minimus dose, mean dose of PTV, Conformity Index(CI),Heterogeneity Index (HI), spinal cord and lung parameters. Further more,thepatients were divided into two groups,the group PTV less than100cc andmore than100cc. There were no significant difference among plan A, plan Band plan C except the mean dose of PTV and Heterogeneity Index (HI), in thegroup PTV less than100cc.Conclusion:(1)Patients with middle section and under thoracic sectionof esophageal carcinoma,under the coplanar and non-coplanar intensitymodulated radiation therapy plan have no significant difference in ConformityIndex(CI) and Heterogeneity Index (HI) condition, non-coplanar intensitymodulated radiation therapy can reduce the V5, V10, V20,V30and mean dose oftotal lung.(2)All the indexes of heart were within the range of clinicallyacceptance, However, they were all significantly higher in the non-coplanarintensity modulated radiation therapy plans, therefore, great care should betaken in applying the non-coplanar intensity-modulated radiation therapy tothe heart-flawed patients.(3)For patients of esophageal carcinoma in cervical and upper thoracic,the non-coplanar intensity modulated radiation therapy plan B was better inHeterogeneity Index (HI) and mean dose of PTV was closer to prescriptiondose, especially in the case of PTV less than100cc.compared with coplanarintensity-modulated radiation therapy plan.Therefore, non-coplanarintensity-modulated radiation therapy plan B has an advantage in these cases.