The Dosimetric Study In Three-dimensional Conformal Radiotherapy And Intensity Modulated Radiotherapy Plans For StageⅢCentral Type Non-small Cell Lung Cancer

ObjectiveTo analyze and compare the characteristics of dose distribution between the three-dimensional conformal radiotherapy(3 D-CRT) and the intensity modulated radiotherapy(IMRT) in stageⅢcentral type non-small cell lung cancer (NSCLC) and to understand which is the optimal plan.Methods32 patients with stageⅢcentral type NSCLC were performed 3D-CRT and IMRT with CMS XIO three-dimensional treatment plan system, respectively. All plans were finished by the same medical physicist, and were evaluated by two radiation oncologist. The prescription dose of 3D-CRT and IMRT was 60Gy/2 Gy /30f. The mean dose delivered to the planning target volume(PTV), the prescribed dose of 95%,100% and 110% occupied the volume percentage of PTV, the target of conformity index and homogeneity index, lungV5, lungV10, lungV20, lungV30, lungV40, mean lung dose, heart V30, heart V40, mean heart dose, the maximum and average exposure dose of spinal cord, the average exposure dose of esophagus, esophagus V35 and esophagus V55 were calculated and analyzed by the dose-volume histogram (DVH) which is obtained the characteristics of target volume and organs at risk (such as:lung, heart, spinal cord and esophagus) in dose distribution.Result(1) Compared with 3D-CRT, IMRT is not only superior in the dose distributions of target volume, but also significantly improves target dose conformity. But IMRT has lower target homogeneity index than 3D-CRT. (2) IMRT have higher lung V5 than 3D-CRT, which is statistically significant (P< 0.05). However, High dose exposure volume of the lung to IMRT in the lung V10, lung V20, lung V30, lung V40 and mean lung dose decreased more than 3D-CRT, especially in the lung V20. The results have statistical difference(P< 0.05). (3) The analysis of heart V30, heart V40 and mean heart dose informed that IMRT has more advantages than 3D-CRT in decreasing the heart exposure dose (P< 0.05). (4) IMRT can significantly decrease the maximum exposure dose and average exposure dose to the spinal cord compared with 3D-CRT(P < 0.05), but neither of the two plans exceed the maximum tolerance dose of spinal cord. (5) IMRT is significantly superior to 3D-CRT in the average exposure dose of esophagus, esophagus V35 and esophagus V55(P< 0.05).ConclusionsCompared with 3D-CRT radiation technique, IMRT effectively enhances the target volume and improve target dose conformity, simultaneously highlights the protective advantages in the organs at risk (such as:lung, heart, spinal cord and esophagus) for stage III central type non-small cell lung cancer.