S2716
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
1031.[2] McNair, H. A., Wedlake, L., Lips, I. M., Andreyev, J., Van Vulpen, M., & Dearnaley, D. (2014) Practical Radiation Oncology, 4(6), 437-447. Keywords: Prostate, enema, rectum
Digital Poster 1857
Comparative Analysis of Setup Errors between Optical Surface Guidance and Skin Mark in Breast Cancer Radiotherapy under DIBH and Free Breathing Huimin Tang 1 , Zhou Jing 2 , Zhen Zheng 1 , Ji Guo 1 , Kaitai Liu 1 1 Radiotherapy, The Affiliated Lihuili Hospital of Ningbo University, Ningbo, China. 2 Radiotherapy, The Affiliated Yangming Hospital of Ningbo University, Ningbo, China Purpose/Objective To compare setup errors between an optical surface monitoring system (OSMS) and conventional skin- mark alignment (CSMA) for radiotherapy following breast-conserving surgery. Translational setup errors, inclouding head-foot (HF), left-right (LR), anterior- posterior (AP) and rotational errors (pitch, roll and yaw) were analyzed to assess the advantages of OSMS for chest wall and tumor bed positioning under deep inspiration breath-hold (DIBH) and free breathing (FB) conditions. Material/Methods A retrospective analysis was conducted on breast cancer patients treated between September 2024 and June 2025 atthe Affiliated Lihuili Hospital and Yangming Hospital of Ningbo University. Setup discrepancies were quantified using CBCT registration. Absolute translational (cm) and rotational (deg) errors were compared using two-sided Wilcoxon rank-sum tests, with multiple-comparisons adjustments using the Benjamini-Hochberg procedure, with significance level set at p<0.05. Sample sizes were as follows: DIBH group: OSMS n=30, CSMA n=30; FB group: OSMS n=42, CSMA n=39. Results In the DIBH group, OSMS significantly reduced LR and AP translations for the chest wall positioning: LR 0.325 (0.225-0.42) cm vs 0.117 (0.075-0.192) cm, p adj < 0.001; AP 0.225 (0.175-0.394) cm vs 0.171 (0.133- 0.200) cm, p adj = 0.0374). For the tumor bed, similar improvements were observed: LR 0.275 (0.181- 0.500) cm vs 0.145 (0.081-0.173) cm, p adj < 0.001; AP 0.275 (0.206-0.375) cm vs 0.200 (0.135-0.267) cm. p adj = 0.0245). No significant differences were found in the HF and all rotational errors between OSMS and CSMA (all p adj > 0.05). In the FB group, OSMS significantly improved AP accuracy from 0.275 (0.171-0.400) cm to
Conclusion: The analysis of 130 CT-scans suggests that enemas are effective to decrease variability of the rectal volume, but not to reduce the rectal volume, in patients treated with a radiotherapy of the prostate in a hypofractionated treatment schedule. Patients with large rectal volumes at diagnostic imaging or with irregular bowel function seem to have the largest clinical benefit. Therefore, we suggest to consider the use of an enema particularly in those patients, as the advantage will very likely outweight the discomfort of an enema [1, 2]. References: [1] Yahya, S., Zarkar, A., Southgate, E., Nightingale, P., & Webster, G. (2013) British Journal Of Radiology, 86,
Made with FlippingBook - Share PDF online