Abstract: Objective To compare the impacts of helical tomotherapy （HT） and two types of volumetric modulated arc therapy （VMAT） planning for the malignant pleural mesothelioma based on the Elekta Synergy linac （S-VMAT） and the Elekta Axesse linac （A-VMAT）， respectively.
MethodsTen patients with inoperable malignant pleural mesothelioma were retrospectively planned with the HT， S-VMAT and A-VMAT. Dose volume histogrambased parameters of the planning target volume （PTV） including the maximum dose （Dmax）， the minimum dose （Dmin）， the average dose （Dmean）， conformity index （CI） and homogeneous index （HI） as well as organs at risks （OARs） were compared among the 3 plans. Results The HT plan provided lower Dmax and Dmean （P＜0.001， P=0.002） while Dmin was similar （P＞0.05）. Compared to S-VMAT and A-VMAT plans， the HT plan showed advantages in HI and CI （HI： 1.04±0.01 vs. 1.11±0.03 vs. 1.09±0.02， P＜0.001； CI： 0.80±0.07 vs. 0.71±0.12 vs. 0.75±0.08， P＞0.05）. As far as the OARs were concerned， the differences among the HT， S-VMAT and A-VMAT plans were not significant （P＞0.05）. In addition， compared to the HT plan, the S-VMAT and A-VMAT plans were more efficient[mean delivery time： （11.11±3.75） min vs. (3.27±1.65)min vs.(2.57±166)min， P＜0.05]. Conclusion VMAT plans are slightly inferior to HT plans in the target dose heterogeneity and conformity. However， the treatment delivery time of the VMAT plans were greatly reduced， which is conducive to improving the patients comfortability and repeatability during the treatment.