3073 - Fan Beam Computed Tomography-Based Online Adaptive Radiation Therapy of Esophageal Cancer: A Feasibility Study from a Single Institution

12:30pm - 01:45pm ET

Poster Hall - Exhibit Hall A

Screen: 3

Presenter(s)

Xiumei Ma, MD - Department of Radiation Oncology, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, Shanghai

X. Xu¹, L. Xu¹, X. Wang¹, L. Rong¹, Z. Diao², X. Wu³, C. Wang⁴, Y. Chi¹, W. Zhang¹, J. Xue¹, and X. Ma¹; ¹Department of Radiation Oncology, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ²Wuhan United Imaging Healthcare Co., Ltd, Wuhan, Hubei, China, ³Shanghai United Imaging Healthcare Co. Ltd., Shanghai, China, ⁴Shanghai United Imaging Healthcare Co., Ltd, Radiotherapy (RT) Business Unit, Shanghai, China

Purpose/Objective(s): Online adaptive radiotherapy (oART) represents a promising strategy to address interfractional anatomical changes during esophageal cancer (EC) treatment. While cone-beam CT (CBCT) and magnetic resonance (MR)-guided oART systems have been described, they are associated with limitations in image quality, procedural efficiency, or patient tolerance. This investigation assesses the feasibility and dosimetric advantages of implementing fan-beam CT (FBCT)-based oART for EC, which offers superior soft-tissue contrast and streamlined workflow.

Materials/Methods: A retrospective analysis was conducted on 18 EC patients who underwent FBCT-guided oART. The prescribed dose was 41.4 Gy. For each treatment fraction, the duration of each oART workflow step was recorded. Dosimetric comparisons between the scheduled (initial) and adapted (re-optimized) plans were performed for target coverage (Planning Target Volume, PTV) and organs-at-risk (OARs) sparing. Statistical significance was evaluated using paired t-tests.

Results:

The mean total duration of the oART workflow was 20.13 ± 6.12 minutes (interquartile range: 15.72 to 23.10 minutes). The adapted plans showed statistically significant improvements in PTV coverage, with increases in D98% and D95% of 10.0% (p=0.01) and 2.7% (p=0.05), respectively. Significant dose reductions to OARs were also achieved. The mean heart dose decreased by 4.9% (p<0.001), with more pronounced benefits observed in patients with lower-segment tumors. Lung doses were reduced, with V20, V5, and mean dose decreasing by 24.4%, 6.9%, and 9.0% (p<0.001), respectively. The gross tumor volume (GTV) exhibited a decreasing trend throughout the treatment course, with an average volume reduction of 28%. Delivery accuracy was verified using in vivo dosimetry based on electronic portal imaging devices (EPID).

Conclusion: FBCT-based oART is a feasible approach for EC radiotherapy, providing measurable dosimetric benefits alongside enhanced image quality and workflow efficiency. Further research is warranted to evaluate its long-term clinical outcomes.