Can Ethos ART Provide an Effective Alternative for Challenging Lung SBRT Situations?
Abstract
Purpose
Patients who undergo stereotactic body radiation therapy (SBRT) for lung cancer can present with contraindications, making it difficult to achieve tumoricidal coverage and adequate organs-at-risk (OAR) sparing. MRI guided-adaptive radiotherapy (MRg-ART) has proven to be an effective method to treat these cases. However, some patients may not be candidates for MRg-ART, or this technology is not an option for institutions. The aim of this case study was to evaluate Ethos ART for lung SBRT patients as an alternate to MRg-ART.
Methods
A stage IA, upper lobe, non-small cell lung cancer patient with a gastric pull-through was treated with Ethos Adaptive SBRT; 10Gy per fraction for 5 fractions, NPO (nothing by mouth) for 4 hours. The patient was not a surgical candidate due previous comorbidity. Due to gastric pull-through, the tumor (ITV) was ~0.3cm away from the stomach. The generated Ethos plan was a custom 11 beam IMRT plan. Each fraction was adapted, due to the stomach proximity. On-couch evaluation of Mobius3D and MobiusFx were used for each treatment.
Results
All 5 fractions of this rare case were treated using ART to minimize the stomach dose. The average (with range) lung PTV D95, PTV V100, ITV D99, and ITV Dmean values were 60%[45.2-76.8], 80%[75.7-86.9], 66.1%[45.2-88], and 109.3%[106.8-113], respectively. The maximum % of the stomach in the PTV is 9.7%, resulting in reduction of ITV or PTV dose coverage. By using ART, we were able to meet the stomach constraints; Dmax and D5cc were maintained at 6.92Gy [6.86-6.93] and 3.91Gy [3.73-4.17]. If the plans were not adapted, the stomach Dmax and D5cc could be 43% and 52.5% higher, respectively, than the physician's intended constraints.
Conclusion
Ethos online adaptive workflow provides an alternate method to treat lung cancer patients with NPO or contraindications for MRg-ART which reduces toxicity to nearby OARs drastically.