Dosimetric study of intensity modulated radiotherapy and volumetric⁃modulated arc radio⁃therapy for cervical cancer with para⁃aortic lymph node metastasis
Objective:To compare dosimetric difference between the intensity modulated radiotherapy(IMRT)and volumetric modulated arc therapy(VMAT)of cervical cancer with para-aortic lymph node metastasis,and to provide the reference basis for selecting the reasonable radiotherapy approach of locally advanced cervical cancer patients. Methods:Twenty patients of cervical cancer with para-aortic lymph node(PALN)metastasis whom confirmed by PET-CT examination and diagnosis and received radiotherapy were selected,and the same CT image was designed by IMRT and VMAT respectively. Then,we compared the parameters of target,organ at risk(OAR),homogeneity index(HI),conformity index(CI),the number of monitor units(MU)and treatment times between two plans. Results:The target dose of IMRT plan and VMAT plan could meet the dosimetric requirement. The CI and HI of planning target volume(PTV) for VMAT plan were superior to IMRT plan(P<0.05). Compared with the IMRT plan,the mean dose of kidney for VMAT plan were lower(P<0.05). The V40 and V50 of the rectum,V40 of the small intestine and the bladder of VMAT plan were better than those of IMRT plan(P < 0.05). The number of MU for VMAT plan(859.92 ± 248.47)were lower than IMRT plan(1 649.50 ± 167.44)(t=11.836,P<0.001). The treatment time for VMAT plan[(304.30 ± 41.98)s]were shorter than IMRT plan[(435.90 ± 37.52)s,t=12.750,P<0.001]. Conclusion:Both of the IMRT and VMAT plans can achieve the clinical dosimetric demands and protect the OARs of cervical cancer with PALN. VMAT has the best performance on CI and HI,and protect the OARs better. VMAT plans have fewer MU and significantly improve the treatment efficiency. Thus it will improve the patient's radiotherapy tolerance,enhance the efficiency of radiotherapy.