Introduction: Cervical cancer has historically been considered the most common cancer among women in the developed world and is still prevalent in less developed countries. The main risk factor for the development of cervical cancer is infection with the human papillomavirus (HPV). For radiation therapy is movement of the irradiation volume a common occurrence. Possible reasons for that are a change in the position of the uterus, bladder, or rectum during irradiation. Variations in bladder volume fill occur between individual irradiations, which in turn affect the position of the irradiation volume. Purpose: To determine the actual need for an ultrasound before each irradiation and the frequency of additional Cone Beam Computed Tomography (CBCT) imaging verification in the irradiation of patients with cervical cancer. Methods: 17 selected patients with cervical cancer who underwent radical irradiation with the Volumetric Modulated Arc Therapy (VMAT) irradiation technique at the Department of Teleradiotherapy of the Institute of Oncology Ljubljana were included in a retrospective study with secondary data analysis. The selected period was between 10 June 2020 and 31 December 2021. The data were analysed using Microsoft Excel 2016 and IBM SPSS Statistics 26. Results: There were no statistically significant differences in the vertical and longitudinal directions, but there was a statistically significant difference between the lateral shifts (left / right). Larger shifts were detected in the anterior, inferior and left directions. There were no statistically significant differences in pitch and roll, only in yaw. There were also no statistically significant differences between clockwise and counterclockwise directions. Discussion and conclusion: We observed that not using ultrasound before each irradiation treatment does not increase the need for additional CBCT imaging verification. Renal function, the effect of radiotherapy on urine output and how the patient follows the instructions about drinking before irradiation also have an influence on adequate bladder filling.
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