Prog Med Phys.  2021 Sep;32(3):70-81. 10.14316/pmp.2021.32.3.70.

Dosimetric Evaluation of Low-Dose Spillage Volumes for Head and Neck Cancer Using Intensity-Modulated Radiation Therapy and Volumetric Modulated Arc Therapy Treatment Techniques

• Kumar G
• Bhushan M
• Kumar L
• Kishore V
• Raman K
• Kumar P
• Barik S
• Purohit S

• KMID: 2521094
• DOI: http://doi.org/10.14316/pmp.2021.32.3.70

Abstract

Purpose
This study was designed to investigate the dosimetric difference between intensitymodulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in head and neck cancer (HNC). The study primarily focuses on low-dose spillage evaluation between these two techniques.
Methods
This retrospective study involved 45 patients with HNC. The treatment plans were generated using the IMRT and VMAT techniques for all patients. Dosimetric comparisons were performed in terms of target coverage, organ-at-risk (OAR) sparing, and various parameters, including conformity index, uniformity index, homogeneity index, conformation number, low-dose volumes, and normal tissue integral dose (NTID).
Results
No significant (P>0.05) difference in planning target volume coverage (D _95% ) was observed between IMRT and VMAT plans for supraglottic larynx, hard palate, and tongue cancers. A decrease in dose volumes ranging from _1Gy to _30Gy was observed for VMAT plans compared with those for IMRT plans, except for V _1Gy and V _30Gy for supraglottic larynx cancer and V _1Gy for tongue cancer. Moreover, decreases (P<0.05) in NTID were observed for VMAT plans compared with that for IMRT plans in supraglottic larynx (4.50%), hard palate (12.80%), and tongue (7.76%) cancers. In contrast, a slight increase in monitor units for VMAT compared with those for IMRT in supraglottic larynx (0.46%), hard palate (2.54%), and tongue (7.56%) cancers.
Conclusions
For advanced-stage HNC, both IMRT and VMAT offer satisfactory clinical plans. VMAT offers a conformal and homogeneous dose distribution with comparable OAR sparing and higher dose falloff outside the target volume than IMRT, which provides an edge to reduce the risk of secondary malignancies for HNC over IMRT.

Keyword

Intensity-modulated radiation therapy; Volumetric modulated arc therapy; Head and neck cancer; Low-dose spillage; Radiotherapy