Reduction of Normal Lung Irradiation in Locally Advanced Non–Small-Cell Lung Cancer Patients, Using Ventilation Images for Functional Avoidance

Abstract

Purpose: To investigate the ability of four-dimensional computed tomography (4D CT)-derived ventilation images to identify regions of highly functional lung for avoidance in intensitymodulated radiotherapy (IMRT) planning in locally advanced non-small cell lung cancer (NSCLC). Methods and Materials:The treatment planning records from 21 patients with stage III NSCLC were selected. Ventilation images were generated from the 4D CT sets, and each was imported into the treatment-planning system. Ninety percentile functional volumes (PFV90), constituting the 10% of the lung volume where the highest ventilation occurs, were generated. Baseline IMRT plans were generated using the lung volume constraint on V20 (<35%), and two additional plans were generated using constraints on the PFV90 without a volume constraint. Dose-volume (DVH) and dose-function (DFH) histograms were generated and used to evaluate the PTV coverage, lung volume, and functional parameters for comparison of the plans. Results:The mean dose to the PFV90 was reduced by 2.9 Gy, and the DFH at 5 Gy (F5) was reduced by 9.6% (SE=2.03%). The F5, F10, V5, and V10 were all significantly reduced from the baseline values. We identified a favorable subset of patients for whom there was a further significant improvement in the mean lung dose.Conclusions: 4D CT-derived ventilation regions were successfully utilized as avoidance structures to reduce the DVH and DFH at 5 Gy in all the cases. In a subset, there was also a Conflict of Interest NotificationThe authors have no commercial or financial interests related to this study to disclose.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access

CT ventilation functional image-based IMRT treatment plans are comparable to SPECT ventilation functional image-based plans

“…Radiotherapy that selectively avoids irradiating highly-functional lung regions may reduce pulmonary toxicity [3][4][5]. This hypothesis is supported by several reports in the literature.…”

Functional image-based radiotherapy planning for non-small cell lung cancer: A simulation study

“…However, a significant proportion of NSCLC patients have defects in regional lung function caused either by local tumour effects or by concurrent pulmonary disease [9][10][11][12]. This observation has prompted investigations of functional image-based radiotherapy planning, utilising physiological information from either single-photon emission computed tomography (SPECT) [10][11][12][13], four-dimensional X-ray computed tomography (4D-CT) [14] or hyperpolarized helium-3 magnetic resonance imaging ( 3 He-MRI) [15,16].…”

“…3 He-MRI avoids the need for additional radiation exposure whilst providing ventilation distribution images comparable to nuclear medicine techniques, and can be co-registered with conventional CT for radiotherapy treatment planning [15,16,18]. Evaluation of lung ventilation has also been proposed through observation of changes in the pulmonary parenchyma across the respiratory cycle using 4D-CT [14]. Both 3 He-MRI and 4D-CT have been combined with IMRT planning, allowing reductions in FV 20 of between 1% and 3% in preliminary studies [14,18].…”

“…Evaluation of lung ventilation has also been proposed through observation of changes in the pulmonary parenchyma across the respiratory cycle using 4D-CT [14]. Both 3 He-MRI and 4D-CT have been combined with IMRT planning, allowing reductions in FV 20 of between 1% and 3% in preliminary studies [14,18].…”

Using 4DCT‐ventilation to characterize lung function changes for pediatric patients getting thoracic radiotherapy

“…4DCT‐ventilation has been gaining momentum in radiation oncology because 4DCT simulations are frequently acquired as part of the standard treatment planning process; which enables the calculation of 4DCT‐ventilation‐based lung function without burdening the patient with an extra imaging procedure. There have been two clinical applications of 4DCT‐ventilation in radiation oncology: functional radiotherapy (designing radiation treatment plans that minimize dose to functional lung) and thoracic treatment assessment 4, 5, 6, 7…”