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Updated: Mar 3, 2026
Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
Pulmonary function after lung tumor stereotactic ablative radiotherapy depends on regional ventilation within
Michael S Binkley1, Martin T King1, Joseph B Shrager2
1Department of Radiation Oncology and Cancer Institute, Stanford University School of Medicine, United States.
Purpose:
To determine if regional ventilation within irradiated lung volume predicts change in pulmonary function test (PFT) measurements after stereotactic ablative radiotherapy (SABR) of lung tumors.
Methods:
We retrospectively identified 27 patients treated from 2007 to 2014 at our institution who received: (1) SABR without prior thoracic radiation; (2) pre-treatment 4-dimensional computed tomography (4-D CT) imaging; (3) pre- and post-SABR PFTs <15months from treatment. We defined the ventilation ratio (VR20BED3) as the quotient of mean ventilation (mean Jacobian-based per-voxel volume change on deformably registered inhale/exhale 4-D CT phases) within the 20Gy biologically effective dose (α/β=3Gy) isodose volume and that of the total lung volume (TLV).
Results:
Most patients had moderate to very severe COPD by GOLD criteria (n=19, 70.1%). Higher VR20BED3 significantly predicted worse change in Forced Expiratory Volume/s normalized by baseline value (ΔFEV1/FEV1pre, p=0.04); n=7 had VR20BED3>1 (high regional ventilation) and worse ΔFEV1/FEV1pre (median=-0.16, range=-0.230 to -0.20). Five had VR20BED3<1 (low regional ventilation) and improved ΔFEV1/FEV1pre (median=0.13, range=0.07 to 0.20). In a multivariable linear model, increasing VR20BED3 and time to post-SABR PFT predicted decreasing ΔFEV1/FEV1pre (R2=0.25, p=0.03).
Conclusions:
After SABR to high versus low functioning lung regions, we found worsened or improved global pulmonary function, respectively. If pre-SABR VR20BED3 is validated as a predictor of eventual post-SABR PFT in larger studies, it may be used for individualized treatment planning to preserve or even improve pulmonary function after SABR.
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