Comparison of dosimetry between extended-field helical therapy and fixed-field intensity-modulated radiation therapy for postoperative cervical cancer

Abstract:

Objective：To compare the dosimetric difference of target areas and organs-at-risk（OAR） between extended-field tomosyn－thesis（HT） and fixed-field intensity-modulated radiation therapy（IMRT） for postoperative cervical cancer. Methods：Twenty patients with extended-field HT who underwent cervical cancer radical surgery from November 2016 to April 2018 in Chongqing University Cancer Hospital were enrolled. The same doctor outlined the target area and OARs（bladder，rectum，intestine bags，the femoral heads，spinal cord and kidneys） and the same physicist designed the HT and IMRT plans separately. Conformity index（CI） of target area，homogeneity（HI），and OAR parameters of two plans were compared. Results：The HI parameter in the HT group（0.06±0.02） was significantly better than that in the IMRT group（0.09±0.03），with statistically significant difference（P=0.000），but the CI parameter in the HT group（0.78±0.05） was slightly lower than that in the IMRT group（0.92±0.04），with statistically significant difference（P=0.000）. OAR parameters in the HT group were superior to those in the IMRT group，except the V40 Gy of intestine pouch in the HT group（83.46 cm3） was greater than that in the IMRT group of 76.29 cm3，with statistically significant difference（P=0.000）. The gradient index（GI） parameter in the HT group was significantly superior to than that in the IMRT group，with statistically significant dif－ference（P=0.000），and the drop in the internal dose was more obvious in the range of 30% to 50%. Conclusion：Both HT and IMRT can meet the clinical needs，but HI of HT has better ho－mogeneity. HT has a preferable advantage for protecting OAR.