Comparison of the Radiation Doses Used in Helical Tomotherapy and Fixed-field Intensity-modulated Radiotherapy for Cervical Cancer

  Objective  To compare the radiation doses applied in helical tomotherapy (HT) and fixed-field intensity-modulated radiotherapy (FF-IMRT) for cervical cancer.

  Methods  The computed tomography (CT) images of 10 patients with cervical cancer were transferred into the Eclipse planning system. HT and FF-IMRT plans were performed on a TomoTherapy treatment planning system(TPS) and an Eclipse TPS, respectively. Institutional dose-volume constraints used in cervical cancer were kept the same for both techniques. The targets and the organs-at-risk were evaluated.

  Results  The coverage of HT planning group and FF-IMRT planning group met the clinical requirements of the prescribed dose. Compared with the FF-IMRT planning group, planning target volume(PTV)95% and PTV100% of HT planning group coverage increased, PTV105% became lower, Dmax and Dmean decreased, conformity index (CI) and homogeneity index (HI) improved(P=0.000). Compared with the FF-IMRT planning group, V₄₀ and Dmax of the bladder reduced by about 7% and 1.7 Gy, respectively(P=0.000); V₄₀ of the rectum reduced by about 8%(P=0.000), V₃₀ and V₄₀ of the small intestine reduced by 4%(P=0.002) and 3%(P=0.000), Dmax reduced by 2 Gy(P=0.000), V₃₀ of the bone marrow increased by 5%(P=0.001), D₅ of the femoral heads showed no difference; Dmax of the cauda equine reduced by 2 Gy(P=0.030); V₂₀, V₃₀, and V₄₀ of the body reduced by 2%, 1.3%, 0.6%, respectively(P < 0.01).

  Conclusions  HT has superior target HI and CI to the FF-IMRT in patients with cervical cancer, along with decreased high-dose regions in the bladder, rectum, and small intestine. Therefore, HT is feasible for the postoperative treatment of cervical cancer patients.