Patterns of care and safety in 1800 patients treated on a high-field MR-Linac platform registry

Abstract

Purpose or Objective In 2018, the first high-field MR-Linac was introduced into clinical practice for the applicability of magnetic resonance guided radiotherapy (MRgRT). This system integrates a diagnostic 1.5 Tesla (T) MR scanner with a linear accelerator and provides online adaptation of treatment plans according to daily position of tumors and organs at risk (OAR) visualised on MR imaging. MRgRT has the potential to increase irradiation doses to the target area, whilst reducing the risk of toxicity by sparing the OARs. Here, we present patterns of care and safety after enrolment of the first 1800 patients in the Multi-OutcoMe EvaluatioN of radiation Therapy Using the MR-Linac Study (MOMENTUM) (NCT04075305). Materials and Methods 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. 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.