Treatment Planning Comparision Of 3-Dimensional Conformal Radiation Therapy And Intensity-Modulated Radiation Therapy Of Esophageal Cancer

Objective: In this study , we compare the difference of treatment plans using 3-dimensional conformal radiation therapy(3D-CRT) and Intensity-modulated radiation therapy (IMRT) of esophageal cancer .The aim is to investigate the characteristics of 3D-CRT and IMRT plans in esophageal cancer and to find out the best technique to achieve improved dose homogeneity and sparing of normal tissues for esophageal cancer.Material and Methods: From March 2006 to July 2007, 6 primary patients with esophageal cancer who treated by 3D-CRT or IMRT were enrooled into this study,All patients need to take several steps including CT scan,target contouring and reconstruction of 3D digital structures before treatment plans were designed,and radiation treatment plans were made by Elekta Precise PLAN 2.11 3D treatment system. The aim of IMRT was as follows: Prescribed dose of 70Gy/30Fx to GTV, 54Gy/30Fx to PTV. V20 of lung=30%, the mean dose (Dmean) of heart=30Gy, the maximum dose(Dmax) to the spinal cord <45Gy. 3D-CRT plans were made according to the same criteria as similar as possible. One 3D-CRT plan was made for each patient with the best dose distribution,while 4 IMRT plans were made with 3,5,7,9 fields and 5 plans altogether for each patient. Evaluation contents include: the target isodose distribution, dose-volume histogram (DVH), conformity index(CI), lung V₂₀,V₃₀, mean lung dose(MLD); Dmean of heart and Dmax to the spinal cord. Statistical analyses were performed by SPSS 13.0 software.Results: Six patients entered this study. All plans were coplanar and total 30 plans were made. All plans could produce good dose distribution for all target volumes. The plans of IMRT5, IMRT7, IMRT9 were more conformal than of CRT4,but IMRT3.Significant differences of CI were obtained among the plans(P=0.004),with the best IMRT9 and worst CRT4.There were also significant differences of lung V₂₀ ,V₃₀ ,MLD (P<0.05) with the lowest of IMRT9,the highest of CRT4.No significant differences were found among the plans in GTV V₉₅, PTV V₉₅, Dmax to the spinal cord and Dmean of heart.Among the cervical and upper thoracic esophageal cancer, Significant differences were found in CI(P<0.05),with the best of IMRT5,IMRT7 and IMRT9,the worst of CRT4 and IMRT3. Significant differences were also found in lung V30(P=0.004), with the lowest of IMRT9,the highest of IMRT3. No significant differences were found among the plans in GTV V₉₅, PTV V₉₅,lung V₂₀,MLD, Dmax to the spinal cord and Dmean of heart.Difference of CI was also significant in mid thoracic esophageal cancer patients(P<0.001),the best was IMRT9,CRT4 was the worst. There were significant differences in lung V₂₀ (P=0.009),V₃₀(P<0.0001),both with the highest of CRT4, the lowest of IMRT9.The lowest of MLD was in the plan of IMRT5,while the highest of CRT4.And lung V20 was above 30Gy in both plans of IMRT3,CRT4. Dmax to the spinal cord was lowest in IMRT3,the highest of CRT4. No significant differences were found among the plans in GTV V₉₅, PTV V₉₅, Dmean of heart.Conclusions:IMRT plan has the advantage in the treatment of esophageal carcinoma with better dose distribution,conformity of target volume and sparing of normal tissues compared to 3D-CRT.Differences of CI were significant in both portions. Lung V₂₀,V₃₀,MLD and Dmax to the spinal cord also had significant differences in plans of mid thoracic lesions. And lung V20 was above 30Gy in both plans of IMRT3,CRT4. IMRT5 and IMRT7 was the best plan considering dosimetric results and clinical practices in this study.