ESTRO 2023 - Abstract Book

S659

Monday 15 May 2023

ESTRO 2023

Conclusion From a dosimetric point of view, it seems feasible to escalate the dose to the target from 41.4 Gy to 50.4 Gy using PRT. In the escalated PRT plans, the MHD and MLD dose remained on average significantly lower than the current standard PhRT plans and did not exceed any OARs constraints. Re-optimisation of the escalated treatment plans might reduce the OARs dose slightly. However, in PhRT the optimisation is restricted by the relatively high heart- and lung dose and its constraints.

Speed Dating: Speed dating

SP-0788

Mini-Oral: Improving the patient experience

MO-0789 Patient experience of head and neck treatment on a 1.5T MRLinac: is our adaptive solution tolerable?

H. Barnes 1 , S. Alexander 2,1 , S. Bhide 1 , A. Dunlop 2,3 , A. Gupta 2 , K. Harrington 2,4 , T. Herbert 1 , K.H. Wong 1 , H. McNair 2,1

1 Royal Marsden NHS Foundation Trust, Radiotherapy, Sutton, United Kingdom; 2 Institute of Cancer Research, Division of Radiotherapy and Imaging, Sutton, United Kingdom; 3 Royal Marsden NHS Foundation Trust, Joint Department of Physics and Radiotherapy, Sutton, United Kingdom; 4 Royal Marsden NHS Foundation Trust, Radiotherapy, London, United Kingdom Purpose or Objective Head and neck cancer (HNC) treatment on the MRLinac (MRL) (Unity, Elekta, Sweden) has recently been developed using the novel adapt-to-shape Lite (ATSlite) method to create clinically acceptable plans clinician-free. There are potential benefits over the adapt-to-position (ATP) method of reducing the need to re-set up patients or replan offline (Gupta et al, 2021). While initial analysis of this technique shows good results (Gupta et al. 2021), it is important to fully investigate patient experience and acceptability of this technique in a larger patient population. Materials and Methods All HNC patients treated with MRI-guided adaptive radiotherapy (MRIG-ART) under the PERMIT trial (NCT03727698), were included in this audit. Data collected included patient demographics, treatment time and patient experience, using an established MRL questionnaire developed and validated by Barnes et al (2021). Questionnaires were completed immediately after fractions 1,2,3 and 30 and a four-point Likert scale (0 – 3, where 2 and 3 represent a positive answer) was used. All HNC patients in PERMIT have a back-up plan created for use on the conventional linac, to prevent missed fractions if the MRL is unavailable or the patient cannot tolerate MRL treatment. The frequency of back-up plan use was collected from the record and verify system (Mosaiq, Elekta, Sweden) and categorised into scheduled, unscheduled-machine unavailability and unscheduled-patient tolerance/side effects. Results Ten of the first 11 HNC patients in the PERMIT trial were included; one patient withdrew from the trial prior to starting radiotherapy. All participants were male with squamous cell carcinomas requiring bilateral neck irradiation. Mean (SD) age was 71.4 (5.2) years. Staging ranged from T2N0M0 to T4aN2M0 (9 oropharynx and 1 larynx) and eight were p16 positive. The mean total treatment time for ATSlite was 40:27 mins, faster than reported mean ATP data (46:00 mins) (McDonald et al, 2021). The percentage of treatments under 60:00 mins was 98.8% (91% for ATP, McDonald et al, 2021). Questionnaire response rate was 85% and individual question response rate was 99%. 96% of responses scored 2 or 3, a positive answer. The lowest scoring question was “I forced myself to manage the situation”, with a mean (SD) of 2.4 (0.9). Three hundred fractions were successfully delivered, 254 (84.7%) on the MRL. The back-up plan was used for 46 fractions: 14 scheduled, 25 unscheduled-machine unavailability and 7 unscheduled-patient tolerance/side effects (n=2 patients). This shows an excellent rate of successful MRL treatment delivery for HNC with minimal disruption attributed to patient tolerance. Conclusion Average treatment times for the ATSlite HNC MRIG-ART are acceptable and faster than previously published ATP treatment times. Patient-reported experience was extremely positive. Use of back-up plans associated with patient tolerance was low. This technique can continue to be used with the confidence that patient experience is not negatively impacted. S.L. Antonetti 1,2 , N. Lambri 1,3 , D. Dei 1,3 , G. Reggiori 3 , C. Franzese 1,3 , S. Tomatis 3 , P. Navarria 3 , C. Galdieri 3 , M. Scorsetti 1,3 , P. Mancosu 3 1 Humanitas University, Department of Biomedical Sciences, Pieve Emanuele-Milan, Italy; 2 Alessandria Hospital, Department of Oncologic Radiotherapy, Alessandria, Italy; 3 IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery Department, Rozzano-Milan, Italy Purpose or Objective Total Marrow Irradiation (TMI) is an intensity modulated technique, evolution of TBI, aiming to irradiate the bones while sparing the neighboring healthy tissues. TMI delivery requires more time than standard RT treatments as the patient's entire body is treated. Therefore, the patient immobilization system is essential for an accurate position reproducibility, MO-0790 Reproducibility of the patient’s extremities positioning in the total marrow irradiation treatment