Extended-field radiotherapy bowel sparing for cervical cancer after surgical staging: Intensity-modulated radiation therapy versus helical tomotherapy

Abstract

BackgroundExtended-field radiotherapy (EF-RT) bowel sparing is attracting interest for cervical cancer after surgical staging. ObjectiveTo ascertain the most efficient technique for bowel sparing by comparing intensity-modulated radiation therapy (IMRT) and helical tomotherapy (TOMO) in EF-RT for treating cervical cancer after surgical staging. MethodsEighteen patients (age: 53.7 ± 2.2 years) with histopathology confirmed as squamous cell carcinoma of the cervix, who received EF-RT after surgical staging in our hospital from November 2016 to April 2018, were collected. The prescription doses to the planning target volume (PTV) were 45 Gy (1.8 Gy per fraction, 5 days a week). The target area and organs-at-risk (OARs) including bladder, rectum, bowel, femoral heads, spinal cord, and kidneys were outlined by the same gynecologic oncologist. The IMRT and TOMO plans were separately designed by the same physicist. We evaluated the dosimetry based on the parameters of PTV and OARs. We also compared the target conformity index (CI), homogeneity (HI), gradient index (GI), and OARs constraints between the two groups. ResultsWe found lower CI, HI, and GI in TOMO than in IMRT (CI: 0.774 ± 0.019 vs. 0.924 ± 0.014; HI: 0.062 ± 0.008 vs. 0.091 ± 0.089; GI: 3.189 ± 0.286 vs. 3.789 ± 0.248, p < 0.001). In terms of GI, the dose dropped from 70% to 30% in vivo, which was evident in TOMO. TOMO also reduced the dose to most of OARs compared with IMRT (p < 0.001). ConclusionsTOMO was superior to IMRT for EF-RT bowel sparing, as it provided better uniformity for the target area and protection for other OARs.