Changes in Non-Small Cell Lung Cancer Tumor Location Secondary to Gastric Distension, Implications in the Context of Stereotactic Body Radiation Therapy

Stereotactic body radiation therapy (SBRT) facilitates highly conformal dose distributions to a targe tumor volume. Accurate tumor localization is extremely important, and lung tumors pose a unique challenge due to respiratory motion. Patients are required to fast before PET/CT but not before CT simulation and daily treatment, introducing potential variability from gastric distension.A case was reviewed involving a patient with early-stage NSCLC which was simulated and treated with SBRT. PET/CT performed while fasting showed an isolated left lower lobe lesion. Following CT simulation, CT and PET/CT images were superimposed for comparison and treatment planning.Tumor location variation was apparent following image superimposition. Simulation CT showed significant gastric distension compared to PET/CT. The patient was resimulated while fasting, resulting in accurate and reproducible tumor localization for treatment planning.Gastric distension can alter tumor location and treatment volumes for radiotherapy planning, possibly resulting in inaccurate treatment administration.