Volumetric-modulated Arc Therapy in Head and Neck Radiotherapy: A Planning Comparison using Simultaneous Integrated Boost for Nasopharynx and Oropharynx Carcinoma

Abstract

Aims: Volumetric-modulated arc therapy (VMAT) allows rapid delivery of radiotherapy. The aim of this planning study was to evaluate VMAT and dynamic intensity-modulated radiotherapy (IMRT) using a simultaneous integrated boost technique

Patients and methods: Planning computed tomography data from 10 patients with locoregionally advanced oropharynx or nasopharynx carcinoma were selected. The prescription dose was 70, 63 and 56Gy to the high-dose, intermediate-dose and low-dose planning target volume (PTV), respectively, and planning parameters were according to Radiation Therapy Oncology Group IMRT protocols. VMAT and IMRT plans were calculated, and dose-volume histograms were created for plan evaluation and comparison.

Results: Clinically acceptable plans were achieved for both IMRT and VMAT plans, although IMRT plans typically required three times the number of monitor units. The coverage of 95% of the PTV70 was between 96 and 100% of the prescribed dose for IMRT plans and 100% for all VMAT plans. There was a trend of improved dose conformity for IMRT plans. Both IMRT and VMAT achieved acceptable plans in terms of sparing of the spinal cord and brainstem. Contralateral parotid sparing was improved with VMAT, with a mean dose of 25.08Gy (range 21.35-30.02Gy) for oropharynx and 31.37Gy (range 23.47-35.52Gy) for nasopharynx cases.

Conclusion: Simultaneous integrated boost VMAT achieved comparable plans to dynamic IMRT in complex head and neck cases and used two-thirds less monitor units.