ESTRO 2020 Abstract book

S1128 ESTRO 2020

Conclusion Haemostatic RT seems to be a safe and effective treatment for patients with end-stage, unresectable advanced gastric-oesophageal cancer. There are no adverse effects with the majority of patients not requiring further blood transfusions. This should continue to be considered for patients with haemetemesis. PO-1928 Initial clinical experience with the MR-Linac System - Patient perspective N. Weitkamp 1 , A. Moreira 1 , J. Day 1 , S. Perryck 1 , L. Wilke 1 , M. Guckenberger 1 , H. Garcia Schüler 1 , S. Tanadini-Lang 1 , N. Andratschke 1 1 University Hospital Zürich, Radiation Oncology, Zürich, Switzerland Purpose or Objective Linear accelerators with integrated MRI have many potential advantages such as enhanced soft tissue contrast, intrafractional imaging and the possibility to adapt the treatment plan daily. However, discussed disadvantages are longer treatment times and the closed environment. This study aimed at evaluating patient experience as well as dropout rates for this new machine. Material and Methods Patients were initially screened for MRI compatibility and claustrophobia by one of the clinicians trained on the MR- Linac. All patients who were referred to the MRIdian™ (Viewray) for treatment were entered into a database to track their treatment progress and given an in-house developed questionnaire consisting of 15 open-ended questions. This contained questions regarding impressions of the machine/room, the experience of lying in the machine and tolerability of treatment duration and position. Median treatment time is 65 minutes. 57 patients treated with the MRIdian system were given questionnaires at the time of MR-Simulation (Sim), 1 st and last treatment to measure patient-reported comfort over time. 117 questionnaires were evaluated. Additionally, patient dropout was monitored to streamline future patient selection as well as optimize machine scheduling. All patients who were referred to simulation were tracked until completion of their course of radiotherapy. Results The length of treatment was acceptable ( ≥7 out of 10) in 84% of responses but only 75% gave the same score to comfort of the treatment position. Patients were comfortable with the feeling of being in a confined space (median 10/10). The 32 patients that received breathing instructions, rated ease of following breathing commands a median score of 9/10, range of 5-10. Although the median change for all questions was 0 points, the largest change in response from any single patient from MR-sim to last treatment was in machine loudness (decrease of 7 points). None of the categories had significant change between sim and last treatment. Patients scored a median of 10/10 for satisfaction with information provided to them before and during their radiation and a median 9.5 for their overall experience. Of the 86 patients referred to MR-sim, 76 completed their appointment due to claustrophobia, tumor visibility and ability to comply with breath-hold (only 1 patient had a screening failure due to implants). 93% of simulated patients completed their first fraction. Only 2 patients (3%) passed their first radiation but were unable to completed all fractions, both due to pain. A total of 68 patients have successfully completed their course of radiotherapy to date. Conclusion After careful patient selection, 94% of simulated patients were able to undergo treatment on the MRIdian System. Treatment was well tolerated and patients scored positively despite the lengthy process of daily adaption and the closed environment. Despite positive feedback, we will strive to further optimize the comfort of the treatment position.

PO-1929 Correlation between dosimetric parameters and acute dermatitis of hypofractionated breast radiation M. Bohli 1 , Z. Fessi 1 , H. Jaffel 1 , S. Tbessi 1 , J. Yahyaoui 1 , R. Moujahed 1 , A. Hamdoun 1 , L. Kochbati 1 1 Abderrahman Mami Hospital, radiation oncology, Ariana, Tunisia Purpose or Objective Skin toxicity is the predominant acute side effect of breast radiotherapy. The aim of this study was to try to find out dosimetry parameters predicting radiation dermatitis Material and Methods Clinical and dosimetric data of 67 breast cancer patients were reviewed. All patients had breast conservative surgery and 3D conformal radiotherapy (mono-isocentric technique) with hypofractionnated regimen (40G/15 fractions + 13.35Gy/5 fractions boost to tumor bed). We defined an organ at risk skin volume and a whole-body volume (which was created by external contour of patient’s up to 3cm above and below the CTV. Skin volume (3 mm thickness) was calculated by “whole body” minus “whole body minus 3 mm” volume. The volumes of the « skin volume »(cm3) receiving 5 Gy, 10 Gy, 15Gy, 20 Gy, 25Gy, 30 Gy, 35Gy, 40 Gy,45Gy,50Gy (V5, V10, V15, V20,V25, V30,V35, V40,V45, V50, respectively) were calculated. Mean and maximal dose to these volumes were also reported. Acute Skin toxicity was monitored during radiotherapy according to CTCAE.4 (common toxicity criteria for adverse events) scale. Dosimetric data of patients with radiation dermatitis grade 2-3 versus grade 0-1 were compared. Results Forty-seven patients (70%) presented with radiation dermatitis grade 0-1. Nineteen patients had grade2 dermatitis and one with grade3. Mean skin volume was 965 cc (593-1526). Table I shows the correlations between the dosimetric parameter and radiation dermatitis grade ≥2. Mean V40Gy was 32cc (± 14.3) for patients with radiation dermatitis G2-3 and 26cc (±10.9) for patients with radiation dermatitis grade0-1 (p=0.04) Grade ≥2 radiation dermatitis was significantly higher for patients with V40>35cm3 than those with V40≤35cm3 (50% vs.22 %, p= 0.038).

Variables

G0-1 (mean) ±SD G2-3 (mean) ±SD p

V5

cm³ 264± 78.7 cm³ 225± 59.3 cm³ 187± 46.3 cm³ 127± 31.9 cm³ 26± 10.9 cm³ 1.4± 1.6

275± 52.8

0.5 0.4 0.3 0.2 0.9 0.9 0.7

V10 V20 V30 V40 V50

237± 39

197± 29.5 136± 24.5 32± 14.3 1.3± 1.3 7.9± 1.5 52.6±2.7

0.04

Dmean Gy 7.9± 0.8

Dmax

Gy 52.4± 2.1

Conclusion Patients with grade ≥2 dermatitis had significantly higher values of V40. Definition of « skin volume » organ at risk during treatment planning would be useful. V40< 35cm3 may be tested as dose volume constraint for grade ≥2 radiation dermatitis PO-1930 Factors influencing clinical trial participation: an assessment for a trial decision aid C. Offermann-Wulms 1 , C. Roumen 1 , A. Ankolekar 1 , A. Van Engelen 1 , R. Fijten 1 , D. De Ruysscher 1 1 MAASTRO Clinic, Department of Radiotherapy, Maastricht, The Netherlands