Helical tomotherapy and two types of volumetric modulated arc therapy: dosimetric and clinical comparison for several cancer sites

Abstract

Radiotherapy accelerators have undergone continuous technological developments. We investigated the differences between Radixact™ and VMAT treatment plans. Sixty patients were included in this study. Dosimetric comparison between the Radixact™ and VMAT plans was performed for six cancer sites: whole-brain, head and neck, lymphoma, lung, prostate, and rectum. The VMAT plans were generated with two Elekta linear accelerators (Synergy®and Versa HD™). The planning target volume (PTV) coverage, organs-at-risk dose constraints, and four dosimetric indexes were considered. The deliverability of the plans was assessed using quality assurance (gamma index evaluation) measurements; clinical judgment was included in the assessment. The mean AAPM TG218 (3%-2mm, global normalization) gamma index valueswere 99.4%, 97.8%, and 96.6% forRadixact™,Versa HD™, andSynergy®, respectively. Radixact™ performed better than Versa HD™ in terms of dosimetric indexes, hippocampi D100%, spinal cord Dmax, rectum V38.4 Gy, bladder V30 Gy,and V40 Gy. Versa HD™saved more of the (lungs-PTV) V5 Gyand (lungs-PTV) Dmean,heartDmean, breasts V4 Gy, and bowel V45 Gy. RegardingSynergy®, the head and neckRadixact™plan saved more of the parotid gland, oral cavity, and supraglottic larynx. From a clinical point of view, for the head and neck, prostate, and rectal sites, theRadixact™ and Versa HD™ plans were similar;Radixact™ plans were preferable for the head and neck and rectum toSynergy®plans. The quality of linac plans has improved, and differences with tomotherapy have decreased. However, tomotherapy continues to be an essential add-on in multi-machine departments.