Uterine Motion Assessed by Daily Cone Beam CT-Scan During Radiation Treatment for Cervical Cancer
Abstract
Introduction: Cervical cancer treatment with external beam radiotherapy (EBRT) is challenged by uterine motion, which can compromise clinical target volume (CTV) coverage. Daily cone-beam computed tomography (CBCT) offers a means to quantify and adapt for inter-fraction displacement.
Methodology: This prospective observational study enrolled six cervical cancer patients undergoing definitive EBRT with concurrent cisplatin, followed by brachytherapy tandem and ovoid. Daily pre-treatment CBCT scans were registered to planning CT images, and maximal uterine displacements were recorded in anterior–posterior (AP), superior–inferior (SI), and right–left (RL) directions. Bladder volumes were measured, and Pearson correlations with motion were calculated.
Results: 150 CBCT scans were evaluated. Mean uterine displacement was greatest in the AP direction (0.96 ± 0.22 cm), followed by SI (0.92 ± 0.17 cm) and RL (0.90 ± 0.13 cm). The largest recorded shifts were 1.27 cm (AP), 1.30 cm (SI), and 1.19 cm (RL). Mean bladder volume during treatment was 330.75 ± 52.95 cm³. AP motion showed a moderate, non-significant correlation with bladder volume (r = 0.357, p≈0.08).
Conclusion: Uterine motion during EBRT for cervical cancer is direction-dependent and influenced by urinary bladder volume, particularly in the AP axis. Daily CBCT enables accurate quantification of motion, supports anisotropic margin design, and facilitates adaptive radiotherapy strategies to ensure optimal CTV coverage while sparing organs at risk.
Conflict of interests: The authors declare no conflict of interest.
Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
License: © Author(s) 2026. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, and unrestricted adaptation and reuse, including for commercial purposes, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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