Abstract:

Objective To investigate the dosimetric comparison between opreoperative fivefield intensity modulated radiotherapy （5F-IMRT） and volumetric modulated arc therapy （VMAT） in the rectum cancer patients with concurrent chemotherapy and radiotherapy. Methods With the application of CMS monaco systems（V2.0，Sweden）， 5F-IMRT and VMAT plans were simulated in 23 rectum cancer patients with preoperative concurrent chemoradiotherapy. The dose characteristic of target volume was evaluated and the dosevolume relationship of small bowel， bladder and bilateral femoral head was compared. Results The CI was similar between the 5F-IMRT（0.810±0.043） and VMAT plans（0.822±0.062）， which could satisfy 95％ of prescribed dose for covered PTV. The HI of the prescribed dose to GTV（1.052±0.019 vs. 1.037±0.008），CTV（1.063±0.016 ^vs. 1.047±0.008） and PTV（1.075±0.020 vs. 1.072±0.018） in the two kinds of plans was similar too. There was no significant difference for the key parameters （D5，Dmin，Dmean and Dmax） of risk organs such as intestine， bladder and femoral head in the two plans（P＞0.05）. There was no significant difference for the key parameters of irradiated volume such as V20，V30，V40 and V50 of risk organs between the 5F-IMRT and VMAT plans（P＞0.05）. Conclusion VMAT plans was as good as 5F-IMRT in the prescribed dose for the target volume， and risk organs such as intestine， bladder and femoral head could be well protected.