Which radiotherapy technique is better for neoadjuvant treatment of rectal cancer: A dosimetric comparison

Abstract

Objective: Our aim was to compare helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) plans with 3-dimensional conformal radiotherapy (3D-CRT) considering the planning target volume (PTV) and organs at risk (OARs) in rectal cancer patients treated with neoadjuvant radiotherapy. Patients and Methods: Thirty patients, previously treated with intensity modulated radiotherapy (IMRT) or 3D-CRT from January 2014 to February 2020 were selected and 3 plans were generated for each patient using VMAT, HT and 3D-CRT. Dosimetric comparisons were made for each plan regarding PTV and OARs. Integral dose (ID) was calculated and beam on times were analyzed. Results: The homogeneity index (HI) was significantly better in HT plans compared with VMAT and 3D-CRT plans (p<0.001), conformity index (CI) was better in VMAT plans. For small bowel, high doses were higher in 3D-CRT plans (p <0.001). HT produced lower doses for the bladder as compared to VMAT and 3D-CRT (p<0.005). The mean and maximum doses of bilateral femoral heads were higher in 3D-CRT plans. Beam on times were longer and IDs were higher in HT plans (p<0.001). Conclusion: Both VMAT and HT improved target homogeneity and conformity and decreased OAR doses compared to 3D-CRT. Although, VMAT was the best method to decrease ID, HT produced better bladder sparing.