Author: Justus Adamson, Wesley Andrew Cunningham, Caleb Logan Smith 👨🔬
Affiliation: Duke University, Duke University Medical Center 🌍
Purpose: Radiation induced bowel toxicity is a persistent issue for abdominal Stereotactic Body Radiation Therapy (SBRT). Remote magnetic navigation systems (RMNS) have been developed for use in magnetic capsule endoscopy which may have potential to be applied to displace mobile organs at risk like bowel during SBRT via strategic placement of the internal magnetic capsule. The purpose of this study is to examine the frequency of cases that would benefit from this application in various SBRT treatments near the gastrointestinal (GI) tract.
Methods: Prior SBRT cases (≤5 fractions) from 2019-2023 were reviewed; prescriptions labeled as liver, pancreas, adrenal, and abdominal were identified and stratified for analysis. The maximum dose to GI tract (small bowel, large bowel, and stomach) and distance to the closest edge of the Planning Target Volume (PTV) on the simulation CT were recorded. Daily CBCT images were also reviewed to quantify interfractional variations.
Results: At simulation, GI tract was within 2cm of the PTV for 16/50, 50/50, 22/28, and 11/14 for liver, pancreas, adrenal, and abdominal SBRT cases, respectively; the GI tract overlapped with the PTV for 7/50, 36/50, 13/28, and 4/14 cases, respectively. Small bowel, large bowel, and stomach were roughly equally likely to be within 2cm of the PTV for liver (11/50, 12/50, and 7/50, within 2cm respectively), and pancreas SBRT cases (49/50, 48/50, and 47/50 within 2cm, respectively); while there was more variation for adrenal (19/28, 11/28, and 14/28, respectively) and abdominal SBRT cases (10/14 and 4/14 within 2cm, for bowel and stomach respectively). Overall, 99/142 (69.7%) of SBRT cases examined exposed healthy GI tissue to high amounts of dose due to proximity (2cm) to the target.
Conclusion: Based on simulation images, a significant portion of radiotherapy plans could benefit from application of RMNS, with the highest potential applicability being pancreas and adrenal SBRT.