Volumetric modulated arc therapy vs 3-dimensional conformal radiotherapy in head and neck cancer: A comparative planning and dosimetry study

Abstract

Objective: In this study, we evaluate the advantages of volumetric modulated arc therapy (VMAT) compared to conventional 3-dimensional conformal radiotherapy (3DCRT) with respect to dosimetry, verification, and treatment efficiency. Methods: Seven patients with locally advanced squamous cell cancer of the head and neck treated by the VMAT and re-planned by 3DCRT techniques were studied retrospectively. The VMAT and 3DCRT plans were evaluated for (i) the homogeneity and conformity of radiation dose to the treatment targets, and (ii) doses to organs at-risk including the spinal cord and parotid glands. The treatment and verification time spent were estimated, so as to compare the efficiency of the VMAT and 3DCRT treatments. Results: The median of the conformity and inhomogeneity indices of planning target volume 60 (to be covered by 60 Gy) were 1.60 and 6.1, respectively for VMAT, and 232 and 14.9, respectively for 3DCRT. The median maximum spinal cord dose of the VMAT plans was 38.9 Gy, compared to 44.5 Gy for the 3DCRT plans. Both parotids of two patients with central tumours could be spared for which the median dose was below 30 Gy. The contralateral parotid of all other patients with unilateral primary tumour could be spared except a patient with a close proximity tumour location. Compared to 3DCRT, the VMAT technique saved 4.25 machine-hours per patient for the full course of radiation treatment. Conclusions: Compared to 3DCRT plans, VMAT plans produced significantly better target coverage as well as dose conformity. Doses to organs at-risk such as the spinal cord and parotid glands were also reduced. Besides, the delivery of VMAT treatment was more efficient. © 2012 Hong Kong College of Radiologists.