Effects of Full-Neck Volumetric Modulated Arc Therapy versus Split-Field Intensity Modulated Head and Neck Radiation Therapy on Low Neck Targets and Structures.

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Effects of Full-Neck Volumetric Modulated Arc Therapy versus Split-Field Intensity Modulated Head and Neck Radiation Therapy on Low Neck Targets and Structures.

Br J Radiol. 2016 Apr 4;:20160009

Authors: Anamalayil SJ, Teo BK, Lin A, Robert LA, Ahn PH

Abstract
OBJECTIVES: While split-field Intensity Modulated Radiation Therapy (SF-IMRT) decreases dose to low neck (LAN) structures such as glottic larynx compared to full-neck IMRT, it is unknown whether SF-IMRT affords superior dose avoidance to organs compared to whole neck-field Volumetric Modulated Arc Therapy (WF-VMAT).
METHODS: Ten patients treated definitively with radiation for oropharyngeal, oral cavity, or nasopharyngeal carcinoma were compared. Only patients ideally suited for SF-IMRT plans were included. Glottic larynx, supraglottic larynx, arytenoids, pharyngeal constrictors, esophagus, brachial plexus and target volume coverage in the low neck were compared between WF-VMAT and SF-IMRT.
RESULTS: VMAT yielded statistically significant decreases in maximum dose to the arytenoids and mean dose to the esophagus. There was no difference in dose to the glottic larynx, supraglottic larynx, pharyngeal constrictors, and the brachial plexus.WF-VMAT led to improved coverage to 50Gy/2Gy fraction equivalent in low neck compared to SF-IMRT using an AP LAN field, but no difference to the 60Gy/2Gy fraction equivalent between SF-IMRT and WF-VMAT using AP/PA LAN boost.
CONCLUSIONS: WF-VMAT affords equivalent glottic and supraglottic larynx dose, and lower dose to the arytenoids and esophagus. WF-VMAT better covers most low neck target structures. Given these findings as well as concerns with matchline cold or hotspots with SF-IMRT, patients requiring comprehensive elective nodal irradiation should typically be treated with WF-VMAT. Advances in Knowledge: Split-field IMRT for larynx-sparing has better dosimetric results to normal structures than whole-neck IMRT, but with increased matchline recurrence risk. We show dosimetric equivalence or superiority of whole-neck VMAT compared to split-field IMRT.

PMID: 27043353 [PubMed - as supplied by publisher]

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