ESTRO 2023 - Abstract Book

S2048

Digital Posters

ESTRO 2023

1 ASST Valle Olona, Radiation Oncology, Busto Arsizio (VA), Italy; 2 ASST Valle Olona, Medical Physics, Busto Arsizio (VA), Italy; 3 ASST Valle Olona, Division of Oncology (Hospital Unit of Saronno), Busto Arsizio (VA), Italy Purpose or Objective Modern radiotherapy treatments of prostate cancer are usually associated to daily positioning verification systems to correct possible random errors and target displacement, with or without intraprostatic radiopaque fiducials. The cone beam computed tomography (CBCT) is the most commonly used system. We investigated the possible advantage of addiction of intraprostatic markers in daily repositioning via CBCT, through the comparison between different operators, and between the same operators over the time. Materials and Methods In our center, the patients treated for prostate cancer undergo daily CBCT, and the treatment includes two possible schemes, 20 or 28 daily sessions. Three CBCT exams were selected for each treatment course, concerning the first, last, and the median. Thirteen patients treated from January to May 2022 were identified, and 39 exams selected. Six patients (46%) had no intraprostatic implanted markers, while 7 (54%) had them. Seven Radiation Oncologists in June 2022 retrospectively reviewed the selected 39 exams, making a second review in September. They recorded the movements of the treatment table to reposition the patient in the correct position with respect to the planning CT, and the time consumed to do it, to identify possible differences in the two setting of patients. Analysis of variance was carried out for comparison of different groups and t- test for unpaired data was used to test difference in mean values of different parameters related to movements (p<0.05 was set as significance level–analysis was made with Microsoft Excel 2013). Results In the first review no statistically significant difference was found between operators in the analysis of image for both groups. A difference between the two groups of patients was only found in mean time for image analysis, shorter in the fiducials group (p=0.03), and, in the mean values of angle correction, higher in the same group (Y° - p=0.04 and Z° - p=0.01). In the second review the difference in mean time for image analysis is no longer different (decrease for the non fiducial group that reach the optimal time as for the fiducial one) while remain a difference between the two groups in the spread (max-min) of angle correction (Y° - p=0.03 and Z° - p=0.003). Conclusion According to our study, the use of intraprostatic seed markers, added to daily CBCT, seems useful to better detect the presence of rotation errors, along the Y and Z axes, allowing their correction. This in very important in particular in prostatic stereotaxic radiation treatments, where the planning target volume is reduced. Time for daily CBCT evaluation seems to be already optimal in the first session for the fiducial group, instead it get better in the following fractions in the other one. Consequently, the use of intraprostatic markers can significantly reduce time to treatment start in extremely hypofractionation radiation treatments, reducing the risk of intrafraction organ motion and target missing. 1 Leo Cancer Care Ltd, Research, Smallfield, United Kingdom; 2 University College London, Department of Medical Physics and Biomedical Engineering, London, United Kingdom; 3 University of Sheffield, College of Health, Well-being and Life Sciences, Sheffield, United Kingdom; 4 Leo Cancer Care Ltd, Research, Sheffield, United Kingdom Purpose or Objective Gantry-free, upright RT using fixed treatment beams is attracting interest worldwide as it promises more cost-effective & compact treatment rooms, for all radiation modalities. Here we investigated whether we could position volunteers in a manner appropriate for upright breast RT, using a robotic patient positioning chair: ‘Eve’ from Leo Cancer Care Ltd. As arms-up treatment positions are known to be uncomfortable for many patients who have undergone breast cancer surgery, we investigated both arms-up & arms-down set-ups. In an attempt to reduce inframammary skin folds (ISF) & associated toxicity we tested the Chabner XRT® Radiation Bra (available commercially from CIVCO Radiotherapy™) & the Support 4 All (S4A) bra (under development at Sheffield Hallam University). Materials and Methods After ethics board review we recruited 7 healthy women, selected to have bra cups>=C (range C:E). A pre-test measurement session was used to determine the volunteers’ nominal bra sizes. On the test day, final fittings & bra selections were performed. Anatomical markers were taped to each woman’s skin to enable estimation of repositioning errors. Perpendicular optical cameras were used to assess these errors (3 repeat tests). A single VacLok bag was moulded for each woman, covering Eve’s seat pan & the lower part of the back-rest. Volunteers were asked to trial: 1) an arms-up position with/without the treatment bras & 2) an arms-down position, topless. The arms-up position was implemented using a Monarch wingboard from CIVCO RT. In total, volunteers spent ~1 hr on Eve, with ~45mins in the arms-up body position. A measuring tape was used to determine upright ISF, with & without the bras. Comfort was assessed using questionnaires & 5-point Likert scales. Results With their arms posed naturally, all volunteers reported that the Eve chair felt comfortable & safe. The arms-down position scored slightly higher in terms of comfort: in particular, one participant who had a pre-existing shoulder condition struggled to maintain the arms-up position. Topless breast repositioning errors for the anatomical markers strongly varied from volunteer to volunteer, ranging from ~1:10mm. Both bras were viewed favourably by the volunteers. With no bra, the mean PO-2278 A pilot study on upright breast RT: positioning volunteers using a robotic chair & specialised bras T. Underwood 1,2 , J. McNamara 3 , J. Nunn 4 , N. Schreuder 1 , H. Probst 3