ESTRO 2022 - Abstract Book

S110

Abstract book

ESTRO 2022

The 1.5 Tesla MR-linac device (Elekta Stockholm, Sweden) is a combination of a diagnostic 1.5 T MRI scanner and 7MV linear accelerator and enables MR-guided radiotherapy (MRgRT) through daily adjustment of treatment plans based on the actual MRI visualized anatomy. Adaptive treatments enable the use of smaller margins thereby including less organs at risk in the irradiated area which potentially reduces toxicity in patients and enables safe dose escalation. However, due to daily adaptation, treatment times are longer compared to conventional treatment and patients need to lie still in a confined bore during treatment delivery. This study aims to evaluate patients’ on-table experience of MRgRT on a 1.5T MR-linac. Materials and Methods All patients treated with a daily adaptive workflow on the MR-Linac at our institution from November 2020 until April 2021, were eligible for inclusion. Patient experience was captured after the third or fourth treatment fraction by means of an adaptation of a validated questionnaire by McNair et al. This questionnaire includes items on physical and psychological coping, and situational and informational needs. Answers to the statements were given on a 5 point Likert scale from strongly disagree to strongly agree. Results In total 83 patients were included in this survey study. Patients were primarily male (n=73, 88%), and the median age of participants was 70 years (range 52-90). The most frequent treatment indications were prostate cancer (n=54, 65%), oligometastatic lymph node (n=9, 11%) and pancreas (n=8, 10%). The median number of fractions was five (range 3-17). Responses to the statements were generally favorable (Figure 1). Ninety percent of patients (n=82) (strongly) agreed to the statement of feeling calm during treatment on MR-Linac. Five (6%) and seven (8%) patients were uncomfortable in the treatment position or on the table respectively. Eight patients (10%) needed more information prior to their treatment and two (2%) patients felt they needed more information during treatment. Four (5%) patients answered (strongly) agreed to ‘I wanted to come out of the treatment machine during my treatment’. Twenty-two (27%) patients felt tingling sensations during their treatment. Conclusion Treatment on the MR-Linac is generally well tolerated. Most patients do not find treatment position uncomfortable, feel sufficiently informed before and during their treatment and tolerate longer treatment times. One in four patients reported tingling sensations during treatment, which warrants further investigation. Purpose or Objective Treatment on an MR-linac can have obvious clinical benefits for some patients, but has potential downsides. Overall treatment time for example, is longer than on a conventional linac. Several studies suggest tolerance for MR-linac treatment is good. However, no direct comparison between MR-linac and conventional linac is available. In this study we investigated the difference in patients’ experiences on both modalities in our clinic. Materials and Methods We used a validated patient experience questionnaire for patients with prostate cancer. This questionnaire contains 16 questions regarding treatment tolerance, and was scored on a four point Likert scale. Questions 1 - 8 were phrased positively, whereas questions 9 – 16 were phrased negatively. This means for questions 1 - 8, a result of 1 was the least favourable and 4 was the most favourable. For questions 9 - 16, this was the opposite. For analysis, responses to questions 9 to 16 were inverted, so that a score of 1 represents the least favourable response and 4 represents the most favourable. Patients were treated either with 5 fractions on the MR-linac or 5, 20, 25 or 30 fractions on a conventional linac. Patients were asked to fill out the questionnaire after their second and last treatment session. Results A total of 93 questionnaires were obtained from 51 patients (MR-linac N = 17, short-course conventional N = 9, long-course conventional N = 25). The mean score for the total questionnaire was 3,78 for the MR-linac (SD = 0,21), 3,65 for short- course conventional (SD = 0,23) and 3,82 for long-course conventional (SD = 0,22), where 4 is the best possible score (range 1 - 4). Overall, 95,64% of the scores were favourable (score 3 or 4) for the MR-linac and 93,73% for the conventional linac. The highest and lowest ranking questions were the same ones for both modalities (see figure 1). Results scored after fraction 2 and after the last fraction were comparable (3,74 and 3,76, respectively. SD = 0,01). A more unfavourable experience for MR-linac treatment, compared to conventional treatment, was only observed for the item ‘’tingling sensations during treatment’’ (12,5% unfavourable responses for the MR-linac versus 0,0% for conventional linac). OC-0134 Patient-reported treatment experience is comparable for MR-linac and conventional linac K. Antonissen 1 , I. van Dijk - Stoltenborg 1 , K. Brouwer - Ezendam 1 , T. Lindeboom - Smit 1 , M. den Hartogh 1 , D. Schuring 1 , P.M. Jeene 1 1 Radiotherapiegroep, Radiotherapy, Arnhem - Deventer, The Netherlands