Quantification and Correlational analysis of Uterine Movement Assessed by Daily Cone Beam CT During Radiotherapy for Cervical Cancer

Background: Cervical cancer treatment with external beam radiotherapy (EBRT) is challenged by uterine motion, which may compromise target coverage. Daily cone-beam computed tomography (CBCT) allows quantification of inter-fraction displacement and may facilitate adaptive treatment strategies. Objective: To quantify inter-fraction uterine displacement in cervical cancer patients undergoing EBRT using daily CBCT and evaluate its relationship with bladder volume and patient-specific factors. Method: This prospective observational study was conducted at a tertiary oncology center in Karachi, Pakistan, after ethical approval. Six patients with intact cervical cancer receiving definitive chemoradiation were recruited through consecutive sampling. Daily pre-treatment CBCT scans were registered with planning CT images to measure uterine displacement in the anterior–posterior (AP), superior–inferior (SI), and right–left (RL) directions. Descriptive statistics were reported as mean ± standard deviation. Pearson correlation was used to assess relationships between variables, with p < 0.05 considered statistically significant. Analysis was performed using SPSS version 22. Results: A total of 150 CBCT scans were analyzed. 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). Maximum recorded displacements were 1.27 cm, 1.30 cm, and 1.19 cm in the AP, SI, and RL directions, respectively. Mean bladder volume during treatment was 330.75 ± 52.95 cm³. AP displacement demonstrated a moderate positive correlation with bladder volume that did not reach statistical significance (r = 0.357, p?0.08). Greater uterine motion was observed among younger, higher-BMI, and multiparous patients. Motion variability was highest during treatment fractions 10–20. Conclusion: Uterine motion during EBRT is direction-dependent and influenced by organ filling and patient-specific factors. Daily CBCT supports accurate motion assessment and may facilitate individualized margin design and adaptive radiotherapy approaches.