Replanning Criteria and Timing Definition for Parotid Protection-Based Adaptive Radiation Therapy in Nasopharyngeal Carcinoma

Yao, Weirong; Xu, Shouping; Liu, Bo; Cao, Xiutang; Du, Liqing; Zhou, Fugen; Feng, Long; Qu, Baolin; Xie, Changchun; Ma, Lin

doi:10.1155/2015/476383

Cited by 25 publications

(42 citation statements)

References 36 publications

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“…And a previous study reported a similar result, with the accumulative average D mean increasing of 11.38% at the end of radiation therapy for all enrolled parotid glands with helical tomotherapy [18]. The sharp increase of the average D mean per fraction for the left parotid gland could be caused by the location of the primary tumors, which were mostly (8/13) located on the left side of the body.…”

Section: Discussionsupporting

confidence: 67%

Clinical study of the time of repeated computed tomography and replanning for patients with nasopharyngeal carcinoma

et al. 2017

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PurposeTo study the necessity of repeat computed tomography (CT) scan and replanning and know a more accurate time using weekly kilovoltage cone beam computed tomography (kV-CBCT) scans for patients with nasopharyngeal carcinoma (NPC) during radiotherapy.Methods and MaterialsThirteen NPC patients treated with IMRT were enrolled into this prospective study. Weekly pretreatment kV-CBCT scans were performed on the 1st, 6th, 11st, 16th, 21st and 26th radiation time, respectively. Target delineations were contoured on all fractionated CBCT images, including the gross tumor volume of the primary nasopharyngeal tumor (GTVnx) and parotid glands. The volumes of GTVnx and parotid glands were calculated automatically using the Pinnacle3 8.0 system. Compared to the original GTVnx, the percentage of shrinking volume (ΔP) ≥ 50% was considered significantly.ResultsAs the radiation proceeding, the GTVnx had a trend of shrinkage. Of all 13 patients, 11 cases (84.6%) had the volume shrinking ≥ 50% before the 21st radiation and 12 cases (92.3%) before the 26th radiation. And the parotid volume decreased significantly in the first four-week radiation, 6.45 ± 3.16cm3 (range, 3.06-13.9cm3) for the left parotid gland and 5.78 ± 2.39cm3 (range, 2.70-11.2cm3) for the right. Furthermore, only a little displacement occurred to bilateral parotid glands.ConclusionThe replanning for NPC patients with IMRT is necessary, and the time between the 21st to 25th radiations is appropriate.

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Section: Discussionsupporting

confidence: 67%

Clinical study of the time of repeated computed tomography and replanning for patients with nasopharyngeal carcinoma

et al. 2017

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“…Treatment plan adaptation in the re-planning situation was evaluated for head and neck cases by several groups [ 10 – 12 ]. The aim was to determine re-planning criteria and timing for plan adaptation.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a software module for adaptive treatment planning and re-irradiation

et al. 2017

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BackgroundThe aim of this work is to validate the Dynamic Planning Module in terms of usability and acceptance in the treatment planning workflow.MethodsThe Dynamic Planning Module was used for decision making whether a plan adaptation was necessary within one course of radiation therapy. The Module was also used for patients scheduled for re-irradiation to estimate the dose in the pretreated region and calculate the accumulated dose to critical organs at risk. During one year, 370 patients were scheduled for plan adaptation or re-irradiation. All patient cases were classified according to their treated body region. For a sub-group of 20 patients treated with RT for lung cancer, the dosimetric effect of plan adaptation during the main treatment course was evaluated in detail. Changes in tumor volume, frequency of re-planning and the time interval between treatment start and plan adaptation were assessed.ResultsThe Dynamic Planning Tool was used in 20% of treated patients per year for both approaches nearly equally (42% plan adaptation and 58% re-irradiation). Most cases were assessed for the thoracic body region (51%) followed by pelvis (21%) and head and neck cases (10%). The sub-group evaluation showed that unintended plan adaptation was performed in 38% of the scheduled cases. A median time span between first day of treatment and necessity of adaptation of 17 days (range 4–35 days) was observed. PTV changed by 12 ± 12% on average (maximum change 42%). PTV decreased in 18 of 20 cases due to tumor shrinkage and increased in 2 of 20 cases. Re-planning resulted in a reduction of the mean lung dose of the ipsilateral side in 15 of 20 cases.ConclusionThe experience of one year showed high acceptance of the Dynamic Planning Module in our department for both physicians and medical physicists. The re-planning can potentially reduce the accumulated dose to the organs at risk and ensure a better target volume coverage. In the re-irradiation situation, the Dynamic Planning Tool was used to consider the pretreatment dose, to adapt the actual treatment schema more specifically and to review the accumulated dose.

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“…Adaptive RT can potentially decrease radiation dose to normal organs and thereby reduce xerostomia and nausea. 26–30 …”

Section: Discussionmentioning

confidence: 99%

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

Hou

Wang

Tsai

et al. 2016

Radiology and Oncology

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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.

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Replanning Criteria and Timing Definition for Parotid Protection-Based Adaptive Radiation Therapy in Nasopharyngeal Carcinoma

Cited by 25 publications

References 36 publications

Clinical study of the time of repeated computed tomography and replanning for patients with nasopharyngeal carcinoma

Clinical study of the time of repeated computed tomography and replanning for patients with nasopharyngeal carcinoma

Evaluation of a software module for adaptive treatment planning and re-irradiation

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

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