A statistical comparison of OAR doses between Helical Tomotherapy and VMAT plans

Head & neck cancer patients have a high risk of nutritional problems caused by both their cancer and the toxic side effects of radiotherapy. The feasibility dose-volume histogram (fDVH) algorithm available in the PlanIQ software (Sun Nuclear Corporation, Melbourne, FL) has been validated to optimally aid in the sparing of certain organs-at-risk (OAR's) in head & neck volumetric modulated arc therapy (VMAT) plans. This study evaluates the met or missed opportunities for limiting dose to OAR's by applying the fDVH tool to head & neck Helical Tomotherapy plans and compare them to VMAT plans of similar dose and staging. Head & neck cancer patients treated in 2014 were selected. All patients had the following OAR's reviewed in an imaging handling software (Mirada Medical, Oxford, UK): larynx, inferior pharyngeal constrictor, submandibular glands, and parotids. Any missing or inadequate contours were edited. Only patients treated with a 70 Gray Simultaneous Integrated Boost Tomotherapy/VMAT plan with a bilateral elective neck were analyzed. Patients with the same or a similar cancer stage as defined by the American Joint Committee on Cancer were grouped, and the differences in areas under the fDVH's and actual DVH's were statistically compared.