Abstract
The risk of radiation-induced toxicity in patients treated for head and neck (HN) cancer with radiation therapy (RT) is traditionally estimated by condensing the 3D dose distribution into a monodimensional cumulative dose-volume histogram which disregards information on dose localization. We hypothesized that a voxel-based approach would identify correlations between radiation-induced morbidity and local dose release, thus providing a new insight into spatial signature of radiation sensitivity in composite regions like the HN district. This methodology was applied to a cohort of HN cancer patients treated with RT at risk of radiation-induced acute dysphagia (RIAD). We implemented an inter-patient elastic image registration framework that proved robust enough to match even the most elusive HN structures and to provide accurate dose warping. A voxel-based statistical analysis was then performed to test regional dosimetric differences between patients with and without RIAD. We identified a significantly higher dose delivered to RIAD patients in two voxel clusters in correspondence of the cricopharyngeus muscle and cervical esophagus. Our study goes beyond the well-established organ-based philosophy exploring the relationship between radiation-induced morbidity and local dose differences in the HN region. This approach is generally applicable to different HN toxicity endpoints and is not specific to RIAD.
Highlights
In radiation therapy (RT) treatment planning (TP), the dose-volume histogram (DVH), introduced in the late 1970s1, has proved to be a valuable tool for summarizing a three-dimensional (3D) dose distribution in a two-dimensional (2D) graph
The current study was designed to apply a VB analysis in order to explore the correlation between radiation induced acute dysphagia (RIAD) and local dose differences in a cohort of patients treated with RT for head and neck (HN) cancer
The patients analyzed in this study are part of a cohort of 100 subjects treated at the Department of Radiation Therapy of the European Institute of Oncology (Milano) for HN tumors, and prospectively evaluated for radiation-induced acute dysphagia (RIAD)
Summary
In radiation therapy (RT) treatment planning (TP), the dose-volume histogram (DVH), introduced in the late 1970s1, has proved to be a valuable tool for summarizing a three-dimensional (3D) dose distribution in a two-dimensional (2D) graph. 2D or 3D methods for dose distribution analysis (dose mapping), collectively referred to as voxel-based (VB) methods, have tried to evaluate local dose response patterns beyond the organ-based philosophy, and have been proposed as alternative approaches to the DVH for identifying dose sensitive regions of normal tissue These methods have been successfully applied to prostate and thoracic cancer patients[3,4,5,6,7,8], but, to the best of our knowledge, no VB analysis has been performed on patients with tumors in the head and neck (HN) area. In HN region, in particular, they proved able to further improve the clinical quality of IMRT plans and OAR sparing[16, 17] Given this background, the current study was designed to apply a VB analysis in order to explore the correlation between radiation induced acute dysphagia (RIAD) and local dose differences in a cohort of patients treated with RT for HN cancer. The application of the VB analysis in HN clinical TP optimization was verified
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