Dosimetric Comparison of Helical Tomotherapy, Volume-Modulated Arc Therapy, and Fixed-Field Intensity-Modulated Radiation Therapy in Locally Advanced Nasopharyngeal Carcinoma.

Shan Lu,Huiqi Fan,Xin Li,Yingying Kuang,Shanshan Yang,Deyang Yu,Xueyuan Hu

doi:10.3389/fonc.2021.764946

Abstract

ObjectiveTo compare the dosimetric parameters of different radiotherapy plans [helical tomotherapy (HT), volume-modulated arc therapy (VMAT), and fixed-field intensity-modulated radiation therapy (FF-IMRT)] for locally advanced nasopharyngeal carcinoma (NPC).MethodsA total of 15 patients with locally advanced NPC were chosen for this retrospective analysis and replanned for HT, VMAT, and FF-IMRT. The prescribed planning target volume (PTV) dose for the primary tumor and metastatic lymph nodes was 70 Gy (2.12 Gy/fraction, delivered over 33 fractions). The prescribed PTV dose for the high-risk subclinical region was 59.4 Gy (1.8 Gy/fraction, delivered over 33 fractions). The dosimetric parameters of the PTV and organs at risk (OARs) and the efficiency of radiation delivery were assessed and compared using the paired-samples t-test.ResultsCompared with VMAT and FF-IMRT plans, HT plans significantly improved the mean conformity index (CI) and homogeneity index (HI). The HT plans reduced the maximum doses delivered to OARs, such as the brainstem, spinal cord, and optic nerves, and significantly reduced the volume delivered to the high-dose region, especially when examining the V 30 value of the parotid glands. However, VMAT reduced the treatment time and improved the efficiency of radiation delivery compared with HT.ConclusionsFor locally advanced NPC, the results showed that HT and VMAT possessed better target homogeneity and conformity, reducing the dose delivered to OARs compared with conventional FF-IMRT, with HT achieving the best effect. Among the techniques studied, VMAT had the shortest radiation delivery time. The results of this study can provide guidance for the selection of appropriate radiation technologies used to treat patients with locally advanced NPC who are undergoing concurrent chemoradiotherapy.

Highlights

Nasopharyngeal carcinoma (NPC) is among the most common head and neck cancer
The helical tomotherapy (HT) plans reduced the maximum doses delivered to organs at risk (OARs), such as the brainstem, spinal cord, and optic nerves, and significantly reduced the volume delivered to the high-dose region, especially when examining the volume that received 30 Gy (V30) value of the parotid glands
For locally advanced nasopharyngeal carcinoma (NPC), the results showed that HT and volume-modulated arc therapy (VMAT) possessed better target homogeneity and conformity, reducing the dose delivered to OARs compared with conventional fixed-field intensity-modulated radiation therapy (FF-intensity-modulated radiation therapy (IMRT)), with HT achieving the best effect

Summary

Introduction

The incidence of NPC has unique geographical and ethnic distribution patterns, with a high incidence in Asia, in Southeast Asia. NPC cases in China represented 48.62% and 50.34% of the incidence and mortality for all cases of Asia in 2012, respectively [2]. 68% of NPC patients suffer from locally advanced disease at the time of diagnosis [3]. Due to the complex anatomy and small region for surgery, the primary treatment modality for NPC is radiotherapy. Early-stage NPC can only be treated with radiotherapy. Advanced NPC is typically treated with concurrent chemotherapy and radiotherapy (CCRT) [4].

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