A Planning Study for Feasibility of Applying Volumetric-Modulated Arc Therapy for Locally Advanced Head and Neck Cancer

Abstract

Purpose: The aim of this study was to investigate the feasibility of applying VMAT for HNC patients in daily practice by comparing volumetric-modulated arc therapy (VMAT) with intensity-modulated radiation therapy (IMRT) for patients with locally advanced head-and-neck cancer (HNC) with regard to the dosimetric parameters and efficiency of delivery.Material & Method: Nine locally advanced HNC patients on either an IMRT or VMAT treatment plan were selected for this study. Another corresponding plan using an alternative technique was generated for comparison. We applied an adaptive strategy with a simultaneous integrated boost (SIB) technique in all radiation therapy protocols, including an initial plan and a reduced plan with acquisition of CT images about 4 weeks later. The Philips Pinnacle³® Planning System v. 9.0 was adopted for designing all treatment plans. Dosimetric parameters compared between VMAT and IMRT plans included target coverage, dose conformity, dose homogeneity, organs at risk (OAR) sparing, monitor units (MUs) and treatment delivery time.Result: The average number of arc used in the VMAT plan was 2.07 and the number of fields per IMRT plan was 6.5. The VMAT and IMRT plans had similar PTV coverage (V100% ＞ 98% and ＞ 96%, respectively). There was no significant difference between VMAT and IMRT in conformity (CI= 1.73 and 1.63, respectively, p= 0.546), homogeneity of PTV-H (HI= 1.08 and 1.07, respectively, p= 0.387), PTV-M (HI = 1.10 and 1.10, respectively, p= 0.891) and PTV-L (HI = 1.13 and 1.12, respectively, p= 0.369). There were similar dose-volume histogram distributions between these two techniques for most of OARs. No significant difference existed in performance of parotid sparing by using these two techniques. Compared to IMRT, VMAT technique significantly reduced the MUs by 16.1% (757.0 versus 635.4 MUs, p= 0.011) and the average treatment time by 4.2 minutes (8.7 versus 4.5 minutes, p ＜ 0.001).Conclusion: This study demonstrated that equally clinical acceptable dose distributions can be achieved in both VMAT and IMRT techniques for HNC. In addition, VMAT provided faster delivery time and lower executed monitor units. Therefore, it is feasible to apply VMAT for HNC for improving the efficiency without compromising the quality of planning dosimetry.