Relative plan robustness of step-and-shoot vs rotational intensity–modulated radiotherapy on repeat computed tomographic simulation for weight loss in head and neck cancer

Journal Article · Fri Jul 01 04:00:00 EDT 2016 · Medical Dosimetry

DOI:https://doi.org/10.1016/J.MEDDOS.2016.01.001· OSTI ID:22577877

Thomson, David J. ^[1]; Beasley, William J. ^[2]; Garcez, Kate; Lee, Lip W.; Sykes, Andrew J. ^[1]; Rowbottom, Carl G. ^[2]

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1. Department of Clinical Oncology, The Christie NHS Foundation Trust, Manchester (United Kingdom)
2. The University of Manchester, Manchester Academic Health Science Centre, Institute of Cancer Sciences, Manchester (United Kingdom)

Introduction: Interfractional anatomical alterations may have a differential effect on the dose delivered by step-and-shoot intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). The increased degrees of freedom afforded by rotational delivery may increase plan robustness (measured by change in target volume coverage and doses to organs at risk [OARs]). However, this has not been evaluated for head and neck cancer. Materials and methods: A total of 10 patients who required repeat computed tomography (CT) simulation and replanning during head and neck IMRT were included. Step-and-shoot IMRT and VMAT plans were generated from the original planning scan. The initial and second CT simulation scans were fused and targets/OAR contours transferred, reviewed, and modified. The plans were applied to the second CT scan and doses recalculated without repeat optimization. Differences between step-and-shoot IMRT and VMAT for change in target volume coverage and doses to OARs between first and second CT scans were compared by Wilcoxon signed rank test. Results: There were clinically relevant dosimetric changes between the first and the second CT scans for both the techniques (reduction in mean D{sub 95%} for PTV2 and PTV3, D{sub min} for CTV2 and CTV3, and increased mean doses to the parotid glands). However, there were no significant differences between step-and-shoot IMRT and VMAT for change in any target coverage parameter (including D{sub 95%} for PTV2 and PTV3 and D{sub min} for CTV2 and CTV3) or dose to any OARs (including parotid glands) between the first and the second CT scans. Conclusions: For patients with head and neck cancer who required replanning mainly due to weight loss, there were no significant differences in plan robustness between step-and-shoot IMRT and VMAT. This information is useful with increased clinical adoption of VMAT.

• OSTI ID: 22577877
• Journal Information: Medical Dosimetry, Journal Name: Medical Dosimetry Journal Issue: 2 Vol. 41; ISSN 0958-3947
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
COMPUTERIZED TOMOGRAPHY
GLANDS
HAZARDS
HEAD
IMAGE PROCESSING
NECK
NEOPLASMS
OPTIMIZATION
PATIENTS
RADIATION DOSES
RADIOTHERAPY
SIMULATION