Adaptive stereotactic body radiation therapy planning for lung cancer.
Abstract
PURPOSE: To investigate the dosimetric effects of adaptive planning on lung stereotactic
body radiation therapy (SBRT). METHODS AND MATERIALS: Forty of 66 consecutive lung
SBRT patients were selected for a retrospective adaptive planning study. CBCT images
acquired at each fraction were used for treatment planning. Adaptive plans were created
using the same planning parameters as the original CT-based plan, with the goal to
achieve comparable comformality index (CI). For each patient, 2 cumulative plans,
nonadaptive plan (PNON) and adaptive plan (PADP), were generated and compared for
the following organs-at-risks (OARs): cord, esophagus, chest wall, and the lungs.
Dosimetric comparison was performed between PNON and PADP for all 40 patients. Correlations
were evaluated between changes in dosimetric metrics induced by adaptive planning
and potential impacting factors, including tumor-to-OAR distances (dT-OAR), initial
internal target volume (ITV1), ITV change (ΔITV), and effective ITV diameter change
(ΔdITV). RESULTS: 34 (85%) patients showed ITV decrease and 6 (15%) patients showed
ITV increase throughout the course of lung SBRT. Percentage ITV change ranged from
-59.6% to 13.0%, with a mean (±SD) of -21.0% (±21.4%). On average of all patients,
PADP resulted in significantly (P=0 to .045) lower values for all dosimetric metrics.
ΔdITV/dT-OAR was found to correlate with changes in dose to 5 cc (ΔD5cc) of esophagus
(r=0.61) and dose to 30 cc (ΔD30cc) of chest wall (r=0.81). Stronger correlations
between ΔdITV/dT-OAR and ΔD30cc of chest wall were discovered for peripheral (r=0.81)
and central (r=0.84) tumors, respectively. CONCLUSIONS: Dosimetric effects of adaptive
lung SBRT planning depend upon target volume changes and tumor-to-OAR distances. Adaptive
lung SBRT can potentially reduce dose to adjacent OARs if patients present large tumor
volume shrinkage during the treatment.
Department
Medical PhysicsSubject
AdultAged
Aged, 80 and over
Cone-Beam Computed Tomography
Dose Fractionation
Esophagus
Female
Humans
Lung
Lung Neoplasms
Male
Middle Aged
Organs at Risk
Radiosurgery
Radiotherapy Planning, Computer-Assisted
Retrospective Studies
Spinal Cord
Thoracic Wall
Tumor Burden
Permalink
https://hdl.handle.net/10161/7295Published Version (Please cite this version)
10.1016/j.ijrobp.2013.05.008Collections
More Info
Show full item record
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Rights for Collection: Masters Theses
Works are deposited here by their authors, and represent their research and opinions, not that of Duke University. Some materials and descriptions may include offensive content. More info