ESTRO 2022 - Abstract Book

S364

Abstract book

ESTRO 2022

This international, multi-institutional, prospective, observational cohort study included patients ≥ 18 years receiving treatment on MR-Linac between February 2019 and October 2021 in eight institutions from five countries. Descriptive statistics were used to describe the patterns of care and safety. Acute severe toxicity was scored according to CTCAE (Common Terminology Criteria for Adverse Events) grade ≥ 3, during first three months after treatment. They were classified as possibly or likely radiation treatment related if the toxicity was not reported pre-treatment, and if nature of adverse event was likely to be related to anatomic area of treatment. Results At present, 1801 patients with complete baseline data were available for analysis. Of these, 1412 patients were male (78%) and the median age was 69 years (range 23-95 years). Tumor sites that were most frequently treated were prostate (n = 789; 44%), lymph nodes (n = 203, 11%) and brain (n = 200, 11%). The majority of patients received treatment for a primary tumor (n = 1284, 71%). Median of fractions per treatment was 5 (range 1-35). Currently, 1011 patients were evaluated for acute toxicity. Grade 3 or more toxicity occurred in 109 patients (11 %), of which 23 (2 %) toxicities were possibly or likely radiation treatment-related. No grade 4 or 5 acute ev ents related to radiation were observed. Image 1: Frequency of inclusions per tumor site

Table 1: Toxicity ( ≥ grade 3 of CTCAE) possibly or likely to be attributed to radiotherapy treatment

Conclusion This study shows acute toxicity outcomes from the fast growing number of patients treated on the MR-Linac for various tumor sites. Given that less than 5 % of grade 3 toxicities, possibly or likely related to treatment, were reported without any grade 4 or 5 events, implementation of high-field online MRgRT is likely to be safe. Updated results will be reported at ESTRO.

OC-0420 Considerations for the clinical implementation of MRI-guided ART for H&N and lung cancers

A. Clough 1 , E. Pitt 2 , C. Nelder 1 , R. Benson 1 , L. McDaid 1 , L. Whiteside 1 , L. Davies 1 , J. Parker 1 , T. Awofisoye 1 , L. Freear 3 , J. Berresford 3 , T. Marchant 3 , A. McPartlin 4 , C. Crockett 4 , A. Salem 4 , D. Cobben 5 , C. Eccles 1