In:
Radiology and Oncology, Walter de Gruyter GmbH, Vol. 50, No. 4 ( 2016-12-1), p. 427-432
Abstract:
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. Patients and methods 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. Results 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 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. Conclusions 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.
Type of Medium:
Online Resource
ISSN:
1581-3207
DOI:
10.1515/raon-2016-0047
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
2016
detail.hit.zdb_id:
2134813-3
