2297 - Zero-Cost Customized Oral Stents Reduce Setup Errors in Nasopharyngeal Cancer Radiotherapy: Secondary Analysis of a Randomized Trial
Presenter(s)
L. Zhang1, F. Bai2, J. Li3, L. Xu4, R. Cai2, Z. Liu5, J. Zang6, and L. Zhao7; 1Department of Radiation Oncology,Xijing Hospital,Air Force Medical University CN, Xi'an, ShaanXi, China, 2Department of Radiotherapy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China, 3Department of Radiation Oncology,Xijing Hospital,Air Force Medical University CN, Xi’an, China, 4Department of Radiation Oncology, Xijing Hospital,Air Force Medical University( Fourth Military Medical University), Xi'an, China, 5Department of Radiation Oncology, Xijing Hospital, Fourth Military Medical University, Xi’an, China, 6Department of Radiation Oncology, Xijing Hospital, Air Force Medical University, Xi'an, China, 7Department of Radiation Oncology, Xijing Hospital, Air Force Medical University, xi an, shan xi, China
Purpose/Objective(s): Conventional radiotherapy immobilization for nasopharyngeal carcinoma (NPC) without oral stents faces challenges in setup reproducibility due to tongue retraction and temporomandibular joint movement, leading to positioning inaccuracies. While universal-design oral stents lack adaptability to individual variations (e.g., mouth-opening capacity), commercial 3D-printed stents are cost-prohibitive and technically complex. This secondary analysis of a prospective randomized controlled trial evaluates the efficacy of a zero-cost, individualized simple oral stent (S-stent) in improving setup accuracy.
Materials/Methods: Baseline data from 99 NPC patients (March 2021–October 2022) were analyzed. Propensity score matching (PSM) balanced 26 S-stent users (experimental group) with 26 non-users (control group). The S-stent, customized using cardboard wrapped in plastic film, was tailored to each patient’s mouth-opening capacity. Setup errors in three dimensions (X: left-right, Y: superior-inferior, Z: anterior-posterior) were measured via cone-beam CT (CBCT) across four regions: overall target, clivus, C4, and C7. Independent t-tests compared intergroup differences.
Results: Post-PSM, both groups (male:female=7:6; age 18–67 years) showed balanced demographics. Among 344 CBCT scans (172 per group), the experimental group demonstrated significantly reduced Y-axis (0.8±0.7 mm vs. 1.4±1.0 mm, p<0.001) and Z-axis (1.0±1.0 mm vs. 1.4±1.1 mm, p=0.018) errors at the clivus. No significant differences were observed in other regions:
- Clivus X: 0.7±7 mm vs. 0.7±0.7 mm (p=0.83)
- C4: X=1.2±2 mm vs. 1.2±0.8 mm (p=0.88); Y=1.2±1.0 mm vs. 1.4±1.0 mm (p=0.20); Z=1.6±1.3 mm vs. 1.4±1.2 mm (p=0.25)
- C7:X=1.7±5 mm vs. 1.7±1.2 mm (p=0.78); Y=1.3±1.0 mm vs. 1.5±1.0 mm (p=0.26); Z=1.7±1.6 mm vs. 1.4±1.3 mm (p=0.18)
- Overall target:X=1.6±1 mm vs. 1.6±1.1 mm (p=0.90); Y=1.2±1.0 mm vs. 1.4±1.2 mm (p=0.21); Z=0.8±0.8 mm vs. 0.8±0.8 mm (p=0.28).
Conclusion: Zero-cost S-stents significantly improve superior-inferior and anterior-posterior setup accuracy at the clivus in NPC radiotherapy. Their simplicity, adaptability, and cost-effectiveness address limitations of universal and 3D-printed stents, offering a practical solution for resource-constrained settings.