<abstract xmlns="http://www.w3.org/1999/xhtml"><sec id="j_raon-2016-0047_s_001_w2aab3b8c70b1b7b1aab1c15b1Aa"><h3>Background</h3><p>Changes in head and neck anatomy during radiation therapy (RT) produce setup uncertainties of nasopharyngeal cancer (NPC) irradiation. We retrospectively analyzed image guidance data to identify clinical predictors of setup errors.</p></sec><sec id="j_raon-2016-0047_s_002_w2aab3b8c70b1b7b1aab1c15b2Aa"><h3>Patients and methods</h3><p>The data of 217 NPC patients undergoing definitive RT on a helical tomotherapy (HT) unit were analyzed. Factors including tumor stage, body mass index, weight loss, and planning target volume (PTV) were assessed as predictors of daily megavoltage computed tomography (MVCT) setup displacements, which were automatically registered using software.</p></sec><sec id="j_raon-2016-0047_s_003_w2aab3b8c70b1b7b1aab1c15b3Aa"><h3>Results</h3><p>Mean daily setup displacements (in mm) were 1.2 ± 0.6, 1.8 ± 0.8, 3.4 ± 1.4 in the medial-lateral (ML), superior-inferior (SI), and anterior-posterior (AP) directions, respectively. Mean weight loss was 4.6 ± 3.3 kg (6.8 ± 4.9%). Patients with weight loss > 5% had significantly larger setup displacements in the AP (3.6 ± 1.5 <italic>vs</italic>. 2.9 ± 1.1 mm, p &lt; 0.001) and SI (1.6 ± 0.7 <italic>vs</italic>. 1.9 ± 0.9 mm, p = 0.01) direction, but not in the ML direction (p = 0.279). The AP setup error increased 0.06 mm (y = 0.055x + 2.927, x: percentage of weight loss/PTV, y: AP displacement) per one percent increase in weight loss normalized to PTV.</p></sec><sec id="j_raon-2016-0047_s_004_w2aab3b8c70b1b7b1aab1c15b4Aa"><h3>Conclusions</h3><p>Patients with weight loss > 5% and smaller PTVs, possibly because of small body frame or neck girth, were more likely to have increased setup errors in the AP direction.</p></sec></abstract>

BackgroundChanges in head and neck anatomy during radiation therapy (RT) produce setup uncertainties of nasopharyngeal cancer (NPC) irradiation. We retrospectively analyzed image guidance data to identify clinical predictors of setup errors.Patients and methodsThe data of 217 NPC patients undergoing definitive RT on a helical tomotherapy (HT) unit were analyzed. Factors including tumor stage, body mass index, weight loss, and planning target volume (PTV) were assessed as predictors of daily megavoltage computed tomography (MVCT) setup displacements, which were automatically registered using software.ResultsMean daily setup displacements (in mm) were 1.2 ± 0.6, 1.8 ± 0.8, 3.4 ± 1.4 in the medial-lateral (ML), superior-inferior (SI), and anterior-posterior (AP) directions, respectively. Mean weight loss was 4.6 ± 3.3 kg (6.8 ± 4.9%). Patients with weight loss > 5% had significantly larger setup displacements in the AP (3.6 ± 1.5 vs. 2.9 ± 1.1 mm, p < 0.001) and SI (1.6 ± 0.7 vs. 1.9 ± 0.9 mm, p = 0.01) direction, but not in the ML direction (p = 0.279). The AP setup error increased 0.06 mm (y = 0.055x + 2.927, x: percentage of weight loss/PTV, y: AP displacement) per one percent increase in weight loss normalized to PTV.ConclusionsPatients with weight loss > 5% and smaller PTVs, possibly because of small body frame or neck girth, were more likely to have increased setup errors in the AP direction.

The ratio of weight loss to planning target volume significantly impacts setup errors in nasopharyngeal cancer patients undergoing helical tomotherapy with daily megavoltage computed tomography

Department of Radiation Oncology, City of Hope National Medical Center, Duarte, California,

Division of Radiation Oncology, Departments of Oncology, National Taiwan University College of Medicine and Hospital, Taipei,

Graduate Institutes of Oncology, National Taiwan University College of Medicine, Taipei,

Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei,

Radiology and Oncology

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

BackgroundChanges in head and neck anatomy during radiation therapy (RT) produce setup uncertainties of nasopharyngeal cancer (NPC) irradiation. We retrospectively analyzed image guidance data to identify clinical predictors of setup errors.Patients and methodsThe data of 217 NPC patients undergoing definitive RT on a helical tomotherapy (HT) unit were analyzed. Factors including tumor stage, body mass index, weight loss, and planning target volume (PTV) were assessed as predictors of daily megavoltage computed tomography (MVCT) setup displacements, which were automatically registered using software.ResultsMean daily setup displacements (in mm) were 1.2 ± 0.6, 1.8 ± 0.8, 3.4 ± 1.4 in the medial-lateral (ML), superior-inferior (SI), and anterior-posterior (AP) directions, respectively. Mean weight loss was 4.6 ± 3.3 kg (6.8 ± 4.9%). Patients with weight loss > 5% had significantly larger setup displacements in the AP (3.6 ± 1.5 vs. 2.9 ± 1.1 mm, p  5% and smaller PTVs, possibly because of small body frame or neck girth, were more likely to have increased setup errors in the AP direction.

BackgroundChanges in head and neck anatomy during radiation therapy (RT) produce setup uncertainties of nasopharyngeal cancer (NPC) irradiation. We...

The ratio of weight loss to planning target volume significantly impacts setup errors in nasopharyngeal cancer patients undergoing helical tomotherapy with daily megavoltage computed tomography

Article Category: Research Article

Published Online: Sep 08, 2016

Page range: 427 - 432

Received: Mar 15, 2016

Accepted: Jul 19, 2016

DOI: https://doi.org/10.1515/raon-2016-0047

© 2016 Radiol Oncol

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.