Dosimetric Comparion Between Helical Tomotherapy And Conventional Linnac-based Intensity Modulated Radiotherapy (IMRT) For Lung Cancer

Background&Obiective:Lung cancer has the highest incidence and mortality among malignant tumor in the world.Radiation therapy is one of the most important treatment for lung cancer and more than 60% of patients have at least once received radiotherapy in the course of the disease.Radiotherapy can improve the local control rate of tumor and prolong the survival time of patients,but radiation pneumonia is a major limiting factor.Radiaction pneumonia has multiple clinical and radiotherapy dosimetric factors,for example: tumor lesion location,lesion size and underlying lung disease,the patient's general condition(KPS),lung V5,V20..Analysis and evaluation of the dosimetric differences between helical tomotherapy(HT)and conventional linnac-based intensity modulated radiotherapy(IMRT)in terms of homogeneity index(HI),conformity index(CI)and dose of organs at risk in the treatment of lung cancer.Methods:27 patients with locally advanced lung cancer were included in the study.Both of HT and IMRT plans were developed for each patient.The dosimetric differences of targets and organs at risk were evaluated,in which the central and peripheral lung cancer patients were stratified.Results: In either the central orperipheral lung cancer group,the conformal index(CI)in HT group was significantly higher than that in IMRT group(P=0.000 ? P=0.036),While V93,V95,V100,V110,Dmean,HI has no significant difference.In terms of organs at risk,in general,HT has a protective effect on the heart,the V30 of heart was lower in HT group than that in IMRT group(t=-3.67?P=0.001)(the result of V30 has no difference in the central lung cancer group,however,the value is 0 in the peripheral lung cancer group which can not be compared statistically).In both of the central and peripheral lung cancer group,the V40,Dmean of heart,V50,Dmean of esophagus,Dmax,Dmean of spinal cord,were not statistically significant.In overall comparison,the difference in V5 of lung was not statistically significant.The V10,V20,V30,V50 of lung in HT were significantly lower than those in IMRT group(P=0.000?P=0.000?P=0.000?P=0.005?P=0.000).In the central lung cancer group,the V5,V10,V20,V30,V50 of lung were significantly lower in HT than those in IMRT group(P=0.016?P=0.000?P=0.000?P=0.000 ? P=0.030).In the peripheral lung cancer group,the V5 of lung was significantly higher in HT than that in IMRT group(P=0.048),the V20,V30,V50 of lung in HT group were significantly lower than those in IMRT group(P=0.001?P=0.013?P=0.019),the difference in V10 of lung was not statistically significant.Conclusion:HT has a better conformal index(CI)comparing to IMRT technology and it also has a better protective effect in heart.In the central lung cancer group,the irradiated volume of lung in HT was lower than that in IMRT group.However,the V5 of lung was higher in HT than that in IMRT group.The irradiated volume of lung in low-dose area increased which should be noted in clinical work.