S2904
RTT- RTT operational practice and workflow innovations
ESTRO 2026
Results: A total of 349, 353, and 459 image sets were acquired from the <350 ml, 350-500 ml, and >500 ml bladder volume groups, respectively. Comparative analysis revealed distinct setup error profiles among the groups. When comparing the <350 ml and 350-500 ml groups, significant differences (P < 0.05) were found in the vertical (VRT) and lateral (LAT) directions, but not in the longitudinal (LNG) direction or rotational (RTN) deviations. The <350 ml group demonstrated superior overall setup reproducibility. For the comparison between the >500 ml and 350-500 ml groups, significant differences (P < 0.05) were observed in VRT, LAT, and rotational deviations. The >500 ml group showed better reproducibility in the VRT and LAT directions but exhibited larger rotational errors. No significant differences (P > 0.05) in translational setup errors (VRT, LNG, LAT) were found between the <350 ml and >500 ml groups. However, the <350 ml group had significantly smaller rotational errors (P < 0.05).
of the prostate. The reactions, seen at varying time points during treatment, are hypothesised to be a combination of skin care and radiotherapy. Skin care instructions effectively reduce symptoms of tissue disorders, which is in line with recently published ESTRO recommendations on radiodermatitis [2]. As a result, our local standardized skin care instructions have been extended to include all pelvic patients, and we encourage other centers to include skin care as part of their patient’s plan of care. References: [1] Institute NC. Common Terminology Criteria for Adverse Events (CTCAE) Version 5. US Department of Health and Human Services, National Institutes of Health, National Cancer Institute; 2017[2] Forde E. et al. Practical recommendations for the management of radiodermatitis on behalf of the ESTRO RTT committee. Radiation Oncology, (2025) 20:46 Keywords: Radiodermatitis, skin care, prostate cancer Influence of Different Bladder Volumes on Setup Errors in Prone Position Radiotherapy for Pelvic Tumors Pengfei Yang, Zhichao Xie, Yiming Wang, Rong Hu, Bo Huang Radiation Oncology, Peking University Shenzhen Hospital, ShenZhen, China Purpose/Objective: To analyze the impact of different bladder volumes on setup errors in pelvic tumor patients undergoing radiotherapy in the prone position. Material/Methods: A total of 43 patients with pelvic tumors (23 rectal cancer, 17 cervical cancer, 3 endometrial cancer) who were treated in the Department of Radiation Oncology at Peking University Shenzhen Hospital between April 2020 and December 2021 were enrolled. All patients were positioned using a Bellyboard. One hour prior to CT simulation and each treatment session, patients consumed 500 ml of water for voluntary bladder filling. They were categorized into three groups based on bladder volume: 13 patients with a volume of <350 ml, 14 with 350-500 ml, and 16 with >500 ml. Before each treatment, a Bladderscan was used to ensure the bladder volume matched. Subsequently, cone-beam computed tomography (CBCT) was performed on the linear accelerator. The acquired CBCT images were registered with the digitally reconstructed radiographs Digital Poster Highlight 887 (DRRs) from the treatment planning system to evaluate setup errors in three dimensions.
Conclusion: Bladder volume significantly influences setup errors in patients receiving prone-position radiotherapy for pelvic tumors. The study indicates that patients with a bladder volume of either <350 ml or >500 ml after self- filling demonstrated smaller setup errors and superior setup reproducibility compared to those with a volume between 350-500 ml. Therefore, it is recommended in clinical practice to maintain a bladder volume below 350 ml for pelvic radiotherapy patients immobilized in the prone position to achieve optimal setup reproducibility.
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