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Improving Lung Stereotactic Body Radiation Therapy Dose Conformity Using a Simple Noncoplanar Volumetric Modulated
Tiffany Kei1, Kirk Luca2, Oluwatosin Kayode2
1Department of Radiation Oncology, Emory University School of Medicine, Atlanta, Georgia; Medical Dosimetry Program, College of Health and Human Sciences, Southern Illinois University Carbondale, Carbondale, Illinois.
Practical Radiation Oncology
|February 27, 2025
Summary
This study shows a new noncoplanar volumetric modulated arc therapy (VMAT) technique improves lung stereotactic body radiation therapy (SBRT) dose conformity, better sparing organs at risk. This VMAT method is now standard practice at our institution.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Lung stereotactic body radiation therapy (SBRT) aims for precise tumor targeting.
- Optimizing dose conformity in lung SBRT is crucial for sparing organs at risk.
- Volumetric modulated arc therapy (VMAT) is an advanced radiation delivery technique.
Purpose of the Study:
- To characterize lung SBRT dose conformity using a novel noncoplanar VMAT technique.
- To compare the dose conformity and organ-at-risk sparing of this VMAT technique against existing clinical plans.
- To identify patient-specific factors influencing dose conformity in lung SBRT.
Main Methods:
- Retrospective replanning of 288 lung SBRT cases using a 2-arc noncoplanar VMAT technique with specific optimization objectives.
- Dose calculation using Acuros, with a focus on Planning Target Volume (PTV) coverage of 95%.
- Evaluation of organ-at-risk doses and conformity index (CI) at various isodose levels, benchmarked against clinical plans using Wilcoxon signed-rank test and linear regression.
Main Results:
- The VMAT technique demonstrated statistically significant improvements in CI across multiple isodose levels (10%-100%), indicating superior dose conformity.
- Average reductions in CI30% and CI50% were 3.5 and 0.63, respectively, with a significant decrease in unacceptable CI50% variations.
- PTV Hounsfield Units and surface-to-volume ratio were identified as significant predictors of dose conformity at CI30%-CI60%.
Conclusions:
- The implemented noncoplanar VMAT technique achieves improved dose conformity and organ-at-risk sparing for lung SBRT.
- This technique is easily implementable and has become the standard of care at the institution.
- The study provides patient-specific insights into dose conformity, supplementing existing clinical trial guidelines for lung SBRT.
