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Magnetic resonance-guided radiotherapy (MRgRT) marks the beginning of a new era. To date, the initial availability of next-generation hybrid magnetic resonance-linear accelerator (MR-Linac) systems is still limited with only 3 such system in Australia. Little is known about the patterns of care and toxicity of treatments on MR-Linac in Australia. Based on an analysis of the first 1000 fractions treated, we report the initial experience at GenesisCare St Vincent’s, Australia.

Patient demographics, disease site, prescribed dose and fractionation scheme, as well as duration of each treatment phase were analysed. Acute toxicity was reported by clinicians according to Common Terminology Criteria for Adverse Events v.5 acute toxicity (within 3 months after the end of treatment). Toxicity data were assessed for patients that consented to participate in the ADAPT-MRL (Analysis of Data to Advance Personalised Therapy with MR-Linac) registry. 

Between June 2020 and September 2021, a total 104 patients were treated with 1099 fractions. Patients were primarily male (83%) with a median age of 69 years (range, 36-90) and were treated for 13 different indications. The most frequent treatment sites were prostate (35%), oligometastatic lymph node (27%), bone (8%), and adrenal gland (8%). The median number of fractions was 5 (range, 3-40). Median prescribed dose was 36.25 Gy (range: 15-50 Gy) in median five fractions (range: 3-5 fractions) for stereotactic ablative RT (SABR) regimens (72%). For non-SABR treatments (28%), the median prescribed dose was 55 Gy (range: 30-80 Gy) in median 25 fractions (range: 6-40 fractions).  Mean total treatment time was 49 minutes and mean beam-on time was 11 minutes for SABR. For non-SABR treatments, mean total treatment time was 37 minutes and mean beam-on time was 6 minutes. Of the 104 patients, 77 consented to be part of the ADAPT-MRL registry. Forty-one patients had complete data on acute toxicity at 3-month follow up, 10 (24%) patients experienced grade 1 & 2 acute toxicity related to treatment. No grade 3, 4 or 5 acute toxicity related to radiotherapy was observed.

In the first 15 months since implementation, patterns of care were diverse with respect to clinical utilisation, treatment sites and prescriptions. Early toxicity outcomes highlight the safety of the treatment. We continue to collect data and evidence on patient reported outcome, toxicity, and safety of this system.