One-Year Analysis of CT Airway Changes Following Thoracic Central SBRT
Abstract
Purpose
The absence of defined dose tolerances and the uncertainty in radiation sensitivity among airway subsegments highlight the need to evaluate imaging-based airway changes in patients receiving radiotherapy for central and ultracentral thoracic tumours. This study aimed to quantify changes in the dimensions of irradiated airways following stereotactic body radiotherapy (SBRT) and compare them to those of non-irradiated airways within the first year post-treatment.
Methods
We retrospectively evaluated 14 patients treated with a single course of SBRT to a central or ultracentral thoracic tumour, analyzing computed tomography (CT) images acquired at the time of radiotherapy simulation and at 4-, 8-, and 12-months following the end of radiotherapy. CT airways were segmented and quantified using VIDA Insights software; anatomically equivalent segmental, subsegmental, and sub-subsegmental airways were utilized to generate airway lumen area (LA) and wall thickness (WT). Irradiated airways were defined as those receiving >100cGy, as determined through registration of the airway tree segmentation and delivered treatment plan in RayStation. Differences in CT airway measurements were evaluated using delta regression analyses, which were adjusted for age, height, body mass index, and CT total lung volume.
Results
Of the 14 patients evaluated, 71% and 29% were treated for central and ultracentral tumours, respectively. The adjusted difference in change in LA from the pre-treatment to 12-months post-treatment between the irradiated and non-irradiated airways was 0.89 mm2 (95% CI -6.4 to 8.1 mm2 [P=0.8]). The adjusted difference in change in WT was -0.09 mm (95% CI -0.4 to 2.6 mm [P=0.6]).
Conclusion
This study is the first to quantitatively report the impact of central and ultracentral SBRT on airway LA and WT measurements, providing important results on initial one-year changes in airway dimensions. Despite its small sample size, the findings demonstrate feasibility and highlight the need for further investigation in this area.