ESTRO 2022 - Abstract Book

S1629

Abstract book

ESTRO 2022

PO-1833 Use of immobilization bra for daily setup of patients with pendulous breast undergoing radiotherapy.

J.Z. Chua 1 , E.P.P. Pang 1 , L.H. Lim 1 , G. Kusumawidjaja 1

1 National Cancer Centre Singapore, Department of Radiation Oncology, Singapore, Singapore

Purpose or Objective This a feasibility study to evaluate the Chabner® Bra as a customized immobilization device for patients with pendulous breast undergoing radiotherapy. Materials and Methods Thirty-four patients with large pendulous breasts were fitted with the Chabner® Bra during CT simulation and treatment procedures (40Gy/15 fractions or /26Gy/5 fractions). A mixed method questionnaire was administered to both radiation therapists (RTTs) and patients to elicit responses from end-users. Staff evaluated the effectiveness of the bra in reducing skin reaction and setup. Patients appraised the bra with regards to the comfort level and ease of wearing. Setup reproducibility was evaluated based on departmental imaging protocol. Acute side effects on the skin were monitored with photo document and assessed using the Radiation Therapy Oncology Group (RTOG) skin toxicity score system during weekly review with oncologists. Results 27 (response rate 79.4%) patients completed the self-administered survey. Majority of the patients (n=23) felt comfortable wearing the bra while 20 patients felt less exposed during treatment. Reproducibility of treatment position was acceptable with a median (range) setup error (isocentre) of 0.0cm (-0.6cm to 0.7cm) (left/right), -0.1cm (-0.5cm to 1.2cm) (posterior) and 0.2cm (-0.5cm to 0.9cm) (inferior) achieved based on matched field borders on skin. However, repeated setups and imaging were required for 3 patients due to large breasts size (cups D-G; size 4-5). Minimal skin toxicity (grade 0-1) were observed for all patients at the end of the treatment. No broken skin or adverse skin reactions were reported throughout the course of treatment. 10 RTTs completed the survey. All male RTTs (n=4) were not confident in assisting patients with the fitting of the bra. 8 RTTs agreed that although it was slightly more difficult to reproduce the breast tissue for daily treatment it has helped patient to maintain the treatment position throughout the procedure. Conclusion The Chabner® Bra has demonstrated feasibility for use as a customized breast immobilization device, with adequate patient comfort and setup reproducibility during breast radiotherapy. With minimal skin toxicity, majority of patients also appreciated the additional modesty when wearing the bra. 1 University of Debrecen, Clinic of Oncoradiology, Debrecen, Hungary; 2 University of Pécs, Faculty of Health Sciences, Doctoral School of Health Sciences, Pécs, Hungary Purpose or Objective Brain metastases (BM) are considered a serious problem regarding the nature of oncological diseases. Radiotherapy, either alone or after surgery, remains the mainstay of treatment for brain metastases. Whole brain radiotherapy (WBRT), stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) could be an option. SRT can be performed with Gamma knife, Cyberknife, tomotherapy and linear accelerator. Modern linear accelerators with integrated image guided radiotherapy (IGRT) solutions such as cone beam computed tomography (CBCT) enabled the extensive use of SRT in the management of BMs. The aim of our work is to demonstrate the role of image guidance and volumetric imaging in stereotactic radiotherapy (SRT) of brain metastases. Materials and Methods Between 2018 and 2020, 106 patients underwent intracranial stereotactic radiotherapy. 10 patients with metastatic brain tumors treated with SRT were randomly selected and included in our study model. Patients were scanned pre- and post- treatment with cone beam CT. This is used to determine the translational and rotational deviations. Rotation values can be corrected up to 2.9°, and for values above 3° the patient must be repositioned. Translational values are corrected to 10 mm, above that the patient needs to be repositioned. Immediately post-treatment, another HR 3D CBCT is performed to assess the intra-fractional displacements. Total of 100 verifications of 50 stereotactic treatments were performed and analyzed. Results Our analysis compared the results of 50 pre-treatment and 50 post-treatment verification CBCT measurements in 10 patients. Population mean X, Y, Z values were -0.13 cm, -0.04 cm, -0.03 cm, respectively, rotation values 0.81°, 0.51°, 0.46°, respectively. Systematic error components for translational displacements pre corrections were as follows: 0.14 cm for X, 0.13 cm for Y and 0.1 cm for Z. Systematic error components of the post-treatment HR 3D CBCTs were as follows: 0.01 cm for X, 0.06 cm for Y and 0.04 cm for Z. Conclusion Frameless immobilization allows fractionation of the treatments but requires a very high degree of accuracy and reproducibility in patient positioning. In our study we evaluated the patient positioning and inter-fractional accuracy of our frameless system. Population mean values close to 0 confirmed that there is no systematic variation in our system and the PO-1834 Cone beam CT verification of mask based immobilization of stereotactic radiotherapy treatments J. Papp 1,2 , M. Simon 1,2 , E. Csiki 1 , Á. Kovács 1,2