ESTRO 2022 - Abstract Book

S271

Abstract book

ESTRO 2022

The result showed the high dose zone to bladder was consistent as the daily adaptative treatment plan even the bladder volume was increased during the treatment. Despite the EPIC Score on urinary function shows significant difference, most of the urinary function returned to baseline level 3 months after treatment. Thus, this bladder preparation protocol was feasible and tolerable for patients undergoing prostate radiotherapy on MRL, which requires a longer treatment duration for online adaptive procedure.

MO-0309 Impact of rectal filling regime on interfractional seminal vesicle changes in prostate radiotherapy

S. Clausen 1 , N. Nyvang Andersen 2 , L.M. Åström 1 , P. Sibolt 1 , D. Sjöström 3

1 Copenhagen University Hospital - Herlev and Gentofte, Dept of Oncology, Copenhagen, Denmark; 2 Copenhagen University Hospital - Rigshospitalet, Dept of Oncology, Copenhagen, Denmark; 3 Copenhagen University Hospital - Herlev and Gentofte, Dept of Oncolgy, Copenhagen, Denmark Purpose or Objective For prostate radiotherapy, the inter- and intrafraction motion of the seminal vesicles (SV) are dependent on rectal filling. The purpose of this study was to evaluate the effect of two different rectal filling regimes on the interfractional movement of the SV. Materials and Methods The interfractional movement of the SV was evaluated for 84 patients and 624 weekly CBCT scans. Two groups of prostate cancer patients with different preparational regimes were retrospectively identified and analyzed. In group A (33 patients and 219 CBCT scans) laxatives were given routinely for all patients before simulation CT and for group B (51 patients and 405 CBCT scans) no laxatives were given, unless indicated based on rectal filling on initial simulation CT. The extent and direction of the SV movement was identified by CT-CBCT evaluation with focus on the SV. It was identified if SV were outside our CTV to PTV margin (5mm in all directions except cranially 8mm). Furthermore, the number of patients that required more than one CBCT/fraction and a new treatment plan during the course of treatment were identified. Results It was possible to evaluate the SV in 89 % of the CBCT scans for the total population (Group A: 192; Group B: 365). Reasons why it was not possible to evaluate the SV was deteriorated image quality due to metal artefacts from hip prothesis and/or artifacts from gas volumes mainly in the rectum. Movement of the SV was identified in 72 % of the CBCT evaluations, and more outliers with movement > 5 mm were observed in group B (14.8 %) compared to group A (13.0 %). In total 11 (13 %) patients had SV identified to be outside the PTV margin at one or more fractions. The relative frequency was higher in group B compared to group A both in number of patients, 15.6 % compared to 9.1 %, and number of fractions, 4.9 % compared to 1.6 %. This is also reflected in the number of patients that required more than one CBCT at some point during treatment, 27 % in group B compared to 12 % in group A, and the number of patients that required a new treatment plan due to lack of SV dose coverage, 7.8 % in group A compared to 3 % in group B. Conclusion This study on interfractional movements in prostate radiotherapy, indicate that a strict rectal filling regime with use of laxatives prior to simulation CT can reduce the clinical workload, both in terms of the number of extra CBCT scans as well as the number of new treatment plans required due to SV movements outside the PTV margins. Purpose or Objective Patient experience has been associated with improvement of treatment compliance and clinical outcomes. Depending on the needs, different measurement approaches exist, including testing by the use of a questionnaire. The aim was to create a patient questionnaire, test the feasibility of a patient reported experience measurement (PREM) and report the patient experiences at the radiation oncology (RO) department of the University Hospital Leuven. Furthermore, a short questionnaire consisting (SQ) of open questions was compared with a long questionnaire (LQ). We analyzed the retrieved data from the questionnaire and developed action points for improvement of the department. Materials and Methods In this prospective study, the used questionnaire was constructed via literature research followed by a proofread of the selected and translated questions by a multidisciplinary team and finished by a pre-test conducted with a selected group of 10 patients which was performed via semi-structured interviews. Between June 2020 and October 2020, 511 patients who finished their radiotherapy treatment received a paper-based questionnaire, consisting of 56 questions, including a SQ with open questions as well as a LQ. Questionnaires were returned anonymously. Descriptive statistics were obtained from the questionnaire using SPSS. Qualitative data were thematically analyzed by NVIVO. Results 308 patients returned the questionnaire (60% response rate) with 261 participants (85%) rating the overall treatment as excellent or very good; 95% of participants would recommend our RO department to a fellow patient. In the qualitative MO-0310 From Patient Reported Experience Measures (PREMs) to improvement actions at the Radiotherapy dept. C. Benazzouz 1 , D. Callens 1 , J. Verstraete 1 , E. Oldenburger 1 , K. Vanhaecht 2 , C. Berghen 1 1 UZ Leuven, Radiation Oncology, Leuven, Belgium; 2 KU Leuven, Leuven Institute for Healthcare Policy, Leuven, Belgium