Comparison of Dosimetric Benefits of Three Precise Radiotherapy Techniques in Nasopharyngeal Carcinoma Patients Using a Priority-Classified Plan Optimization Model.

Qiaoli Wang,Jiang Wu,Ruixue Cao,Tianrui Xu,Lixiu Zhu,Guoqiang Xu,Wenhui Li,Wei Jiang,Jiawen Yan,Sijin Zhu,Wei Xiong,Jiyong Qin

doi:10.3389/fonc.2021.646584

Abstract

IntroductionAlthough intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and tomotherapy (TOMO) are broadly applied for nasopharyngeal carcinoma (NPC), the best technique remains unclear. Therefore, this study was conducted to address this issue.MethodsThe priority-classified plan optimization model was applied to IMRT, VMAT and TOMO plans in forty NPC patients according to the latest international guidelines. And the dosimetric parameters of planning target volumes (PTVs) and organs at risk (OARs) were compared among these three techniques. The Friedman M test in SPSS software was applied to assess significant differences.ResultsThe median PGTVnx coverage of IMRT was the lowest (93.5%, P < 0.001) for all T categories. VMAT was comparable to TOMO in OARs clarified as priority I and II, and both satisfied the prescribed requirement. IMRT resulted in a relatively high dose for V25 and V30. Interestingly, subgroup analysis showed that the median PTV coverage of the three techniques was no less than 95% in the early T stage. The heterogeneity index (HI) of PGTVnx in VMAT was better than that in IMRT (P = 0.028). Compared to TOMO, VMAT showed a strong ability to protect eyesight and decrease low-dose radiation volumes. In the advanced T stage subgroup, TOMO numerically achieved the highest median PGTVnx coverage volume compared with VMAT and IMRT (93.61%, 91% and 90%, respectively). The best CI and HI of PCTV-1 were observed in TOMO. Furthermore, TOMO was better than VMAT for sparing the brain stem, spinal cord and temporal lobes (all P < 0.05). However, the median V5, V10, V15, V20 and V25 were significantly higher with TOMO than with VMAT (all P < 0.05).ConclusionIn the early T stage, VMAT provides a similar dose coverage and protection of OARs to IMRT, and there are no obvious advantages to choosing TOMO for NPC patients in the early T stage. TOMO may be recommended for patients in the advanced T stage due as it provides the largest dose coverage of PGTVnx and the best protection of the brain stem, spinal cord and temporal lobes. Additionally, more randomized clinical trials are needed for further clarification.

Highlights

Intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and tomotherapy (TOMO) are broadly applied for nasopharyngeal carcinoma (NPC), the best technique remains unclear
In the early T stage, VMAT provides a similar dose coverage and protection of organs at risk (OARs) to intensity-modulated radiotherapy (IMRT), and there are no obvious advantages to choosing TOMO for NPC patients in the early T stage
TOMO may be recommended for patients in the advanced T stage due as it provides the largest dose coverage of PGTVnx and the best protection of Comparison of IMRT, VMAT, and TOMO in NPC

Summary

Introduction

Intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and tomotherapy (TOMO) are broadly applied for nasopharyngeal carcinoma (NPC), the best technique remains unclear. NPC arises in a deep anatomical location, adjacent to many important organs, and tumor cells are extremely sensitive to radiotherapy. Radiotherapy is an important means of anticancer therapy for NPC. Recent studies have shown that the 5-year survival rate of NPC patients ranges from 77.2% to 89.7%, with radiotherapy as the cornerstone of comprehensive treatment [4,5,6]. Compared with the two-dimensional radiotherapy (2D-RT) technique, three-dimensional radiotherapy (3D-RT) technique has resulted in better survival rates, lower levels of damage to normal structures and better conformity of tumor targets in patients diagnosed with NPC [7, 8]

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