PRACTICAL ONCOLOGY JOURNAL ›› 2018, Vol. 32 ›› Issue (4): 327-332.doi: 10.11904/j.issn.1002-3070.2018.04.008

• Clinical Application • Previous Articles     Next Articles

Preliminary study on fixed dose rate volumetric modulated intensity radiotherapy in postoperative patients with rectal cancer

CHEN Xiang1,2,ZHOU Jianliang1,WANG Binbing2,LI Pu2,SHAN Guoping2   

  1. 1.Department of Nuclear Science and Technolory,University of South China,Hengyang 421001,China;
    2.Department of Radiotherapy Physics/Key Laboratory of Tumor Radiation Therapy,Zhejiang Cancer Hospital
  • Received:2018-04-01 Online:2018-08-20 Published:2018-09-06

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Abstract: Objective The objective of this study was to investigate the feasibility of fixed dose rate volumetric modulation in pelvic radiotherapy after rectal cancer surgery. Methods Ten patients with rectal cancer radiotherapy were enrolled in this study.The RayStation planning system was used to establish a variable dose rate volumetric modulation(VDR-VMAT),a fixed dose rate volume modulation(CDR-VMAT),and a 5-field static intensity modulated radiation therapy(5F-sIMRT)plans for each patient.Dose volume histograms were used to evaluate the dosimetric parameters of the three planned target area,endangered organs and normal tissue,and to assess the total machine hop count(MU)and planned execution time. Results In terms of target area dose,CDR-VMAT compared to VDR-VMAT,D2%,Dmean,D98%,HI and CI were similar;CDR-VMAT compared to 5F-sIMRT D2%,Dmean,D98%,HI and CI all had statistically significant differences(P＜0.05).In the aspect of OARs,CDR-VMAT compared with VDR-VMAT,all parameters of bladder,small intestine,left and right femoral head were similar;CDR-VMAT compared with 5F-sIMRT,Dmean,V40 of the bladder,Dmean,Dmax of the small intestine,Dmean of the left and right femoral head all had statistically significant differences(P＜0.05).For the normal tissue,CDR-VMAT compared with VDR-VMAT,V5,V10,V15,V20,V25 and V30,were similar;CDR-VMAT compared with 5F-sIMRT,V5,V15 and V30 all had statistically significant differences(P＜0.05).The MU of the CDR-VMAT plan was 16.44% higher than that of VDR-VMAT and 24.45% higher than that of 5F-sIMRT.The execution time of the CDR-VMAT plan was nearly double than that of VDR-VMAT but shorter than that of 5F-sIMRT. Conclusion CDR-VMAT can form a high quality plan as VDR-VMAT with better target coverage,endangering organ protection and low dose exposure volume of normal tissue than 5F-sIMRT.However,the CDR-VMAT plan has more MU than VDR-VMAT and 5F-sIMRT.The execution time of CDR-VMAT is longer than VDR-VMAT and slightly shorter than 5F-sIMRT.The lower initial cost of the CDR-VMAT is expected to provide additional options for rotating radiotherapy for linear accelerators that do not have variable dose rate.

Key words: Rectal cancer, Volumetric modulated arc therapy, Step and shot intensity modulated, Variable dose rate, Constant dose rate

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