Author: Samira Dabaghmanesh, Beth A. Erickson, William Hall, Jason Hirshberg, An Tai 👨🔬
Affiliation: Department of Radiation Oncology, Medical College of Wisconsin 🌍
Purpose: Treatment plan evaluation for minimizing duodenal toxicity often involves multiple dose-volume constraints that vary based on fractionation. The Equivalent Uniform Dose (EUD) has emerged as a valuable predictor of toxicity due to its ability to incorporate the entire dose-volume histogram into its calculation and its independence from fractionation. This study evaluates the correlation between EUD and duodenal toxicity and assesses the EUD performance as a predictive metric for pancreatic cancer patients.
Methods: A retrospective analysis was conducted on 22 patients with locally advanced pancreatic cancer (LAPC) treated at our clinic between 2016 and 2021. six patients were treated on a 1.5T MR-LINAC, while the remaining were treated on a regular LINAC. Radiation doses of 50.4 Gy-51.15 Gy in 28-31 fractions (fx) were prescribed to the elective CTV, and a SIB was delivered at 2.25Gy/fx from 63Gy/28fx up to 69.75Gy/31fx to the GTV, depending on OAR constraints. All received concurrent chemotherapy. Of these, nine patients experienced G2+ toxicity, while 13 did not. Duodenal EUD was calculated using MIM software and the linear-quadratic (LQ) model, employing organ-specific radiobiological parameters such as α/β ratio and n (the volume effect of the organ at risks) extracted from clinical data fitting in our prior study. Additionally, the correlation of the D(0.03cc) dose to duodenum with toxicity was analyzed to compare its predictive performance against that of EUD.
Results: Our analysis revealed a strong correlation between EUD and duodenal toxicity. Statistical testing demonstrated that EUD, with a p-value of 0.041, is a more significant predictor of toxicity compared to D(0.03cc), which had a p-value of 0.466.
Conclusion: EUD is a robust and significant predictive metric for duodenal toxicity in pancreatic cancer patients. As a single, highly correlated measure, EUD offers promise for integration into radiation treatment planning to enhance the precision of toxicity risk assessment.