Evaluation of unified intensity-modulated arc therapy for the radiotherapy of head-and-neck cancer

Michael MacFarlane; Douglas A Hoover; Eugene Wong; Nancy Read; David Palma; Varagur Venkatesan; Alex Hammond; Jerry J Battista; Jeff Z Chen

doi:10.1016/j.radonc.2016.03.010

Evaluation of unified intensity-modulated arc therapy for the radiotherapy of head-and-neck cancer

Radiother Oncol. 2016 May;119(2):331-6. doi: 10.1016/j.radonc.2016.03.010. Epub 2016 Mar 31.

Authors

Michael MacFarlane¹, Douglas A Hoover², Eugene Wong³, Nancy Read⁴, David Palma², Varagur Venkatesan⁴, Alex Hammond⁴, Jerry J Battista², Jeff Z Chen²

Affiliations

¹ Department of Medical Biophysics, Western University, London, Canada; London Regional Cancer Program, London Health Science Center, LondonCanada. Electronic address: mmacfar4@uwo.ca.
² Department of Medical Biophysics, Western University, London, Canada; London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.
³ Department of Medical Biophysics, Western University, London, Canada; Department of Oncology, Western University, London, Canada; Department of Physics & Astronomy, Western University, London, Canada.
⁴ London Regional Cancer Program, London Health Science Center, LondonCanada; Department of Oncology, Western University, London, Canada.

PMID: 27041142
DOI: 10.1016/j.radonc.2016.03.010

Abstract

Purpose: Recently our group developed a unified intensity-modulated arc therapy (UIMAT) technique which allows for the simultaneous inverse-optimization and the combined delivery of volume-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT). The aim of this study was to evaluate the dosimetric benefits of UIMAT plans for radiation treatment of complex head-and-neck cancer cases.

Methods and materials: A retrospective treatment planning study was performed on 30 head-and-neck cases, 15 of which were treated clinically with VMAT while the other 15 were treated with step-and-shoot IMRT. These cases were re-planned using our UIMAT technique and the results were compared with the clinically delivered plans. Plans were assessed in terms of clinically relevant metrics describing target volume coverage, dose conformity, and the sparing of organs at risk.

Results: When compared to stand-alone VMAT or IMRT, UIMAT plans offered slightly better tumor volume coverage (Median D95: 98.1% vs. 97.5%, p=0.01) and similar dose conformity (Median CI: 0.69 vs. 0.69, p=0.09). More significantly, UIMAT plans had substantially lower doses to all organs at risk, including the spinal cord (Median D2%: 29.9Gy vs. 35.6Gy, p<0.01), brainstem (Median D2%: 21.2Gy vs. 25.6Gy, p<0.01), left parotid (Median DMean: 26.1Gy vs. 28.0Gy, p<0.01), and right parotid (Median DMean: 23.6Gy vs. 27.2Gy, p<0.01). The reduction in OAR doses did not result from the redistribution of dose to unspecified tissue. Furthermore, UIMAT plans can be delivered with comparable delivery times to VMAT (Median time: 135s vs. 168s, p=0.394) but with fewer monitor units (Median MU: 486 vs. 635, p<0.01).

Conclusions: Compared to stand-alone IMRT or VMAT, UIMAT was demonstrated to have a dosimetric advantage for the radiation treatment of head-and-neck cancer.

Keywords: Head-and-neck cancer; IMRT; Radiotherapy optimization; UIMAT; VMAT.

MeSH terms

Head and Neck Neoplasms / pathology
Head and Neck Neoplasms / radiotherapy*
Humans
Organs at Risk
Parotid Gland / radiation effects
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods
Radiotherapy, Intensity-Modulated / methods*
Retrospective Studies
Tumor Burden