ORIGINAL RESEARCH article
Front. Oncol.
Sec. Radiation Oncology
Dosimetric Impact of Endoscopic Titanium Clips in Photon and Proton Radiotherapy for Esophageal Cancer
NingJing Siah 1
Wang Xiaohui 1
Xin Li 2
PengYuan Qi 1
BingYue Wang 1
Rui Zhou 1
ChuanChuan Yu 3
Jun Han 1
Xiaorong Dong 1
Sheng Zhang 1
1. Wuhan Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
2. Yichang Second People's Hospital, Yichang, China
3. Sun Yat-Sen University, Guangzhou, China
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Abstract
Abstract Background To quantitatively assess the dosimetric influence of endoscopic titanium clips in photon and proton radiotherapy for esophageal cancer and determine whether clip-induced heterogeneities affect target coverage, esophageal wall dose, or plan robustness. Methods This retrospective study included 26 patients with esophageal squamous cell carcinoma who underwent metallic clip placement for radiotherapy localization. Photon IMRT/VMAT and proton pencil beam scanning plans were generated with clip densities represented either by native CT values or overridden to 0 HU. Multiple regions of interest, including the clip, 3-mm and 5-mm expansions and their intersections with the esophageal wall, GTV, and PTV, were evaluated. Dose–volume parameters were compared using paired tests and linear mixed-effects models. Proton plans incorporated robust optimization accounting for ±5 mm setup and ±3.5% range uncertainties. Results Clip-induced perturbations were small and localized in both modalities. Photon dose differences were ≤0.3 Gy across evaluated structures, while proton variations were ≤0.1 Gy, confined to the immediate clip vicinity. Target coverage remained stable, with all changes ≤1% of the prescription dose. Proton robustness was preserved under uncertainty scenarios, maintaining ≥95% CTV coverage. Differences between modalities were minimal, and although a few metrics reached statistical significance, the absolute dose changes remained small. Esophageal wall dose increases did not exceed 0.2 Gy (<0.5% of prescription), well below established toxicity thresholds. Conclusion Endoscopic titanium clips introduce only minor, clinically insignificant dose perturbations in photon and proton esophageal radiotherapy. Proton sensitivity to local heterogeneities is effectively mitigated by robust optimization. These findings support the dosimetric safety and reliability of titanium clips as localization markers in contemporary treatment planning.
Summary
Keywords
Dose perturbation, esophageal cancer, Photon radiotherapy, Proton radiotherapy, Titanium clips
Received
17 December 2025
Accepted
19 February 2026
Copyright
© 2026 Siah, Xiaohui, Li, Qi, Wang, Zhou, Yu, Han, Dong and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Jun Han; Xiaorong Dong; Sheng Zhang
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