ESTRO 2022 - Abstract Book

S363

Abstract book

ESTRO 2022

Univariate and multivariate analyses were performed on the combined cohort to test for an association between nodal status, T stage, age, receipt of neoadjuvant chemotherapy (NAC) and OS. Results 245/369 patients with cN+M0 bladder cancer in the International cohort had OS data for comparison. At the UK centre, 52 patients received radical intent treatment with either surgery (n=18) or RT (n=34). OS was compared between the 3 cohorts (Figure 1). Median OS was 3.84 (2.28-NA), 1.85(1.05-NA) and 1.93(1.62-NA) years for the International, UK Surgery and RT groups respectively however a Log rank test showed no overall survival difference between the 3 cohorts ( χ 2 =3.2, 2 df, p=0.2).

In a univariable analysis OS positively associated with age <70 (HR 0.70 (0.49-0.98) p=0.04) and receiving NAC (HR 0.44 (0.31-0.62) p=0.28) and negatively associated with T stage 3 or 4 (HR 1.67 (1.14-2.44) p=0.01). Nodal stage (N1 vs N2/3) and Cohort (International vs UK) showed no statistically significant association with OS. Only NAC retained a significant association with OS within a multivariate analysis. Conclusion Our retrospective data does not find a significant difference in OS between cohorts receiving radiotherapy and surgery. Limitations in our data are the risk of confounders when comparing retrospective cohorts and the smaller number of RT patients with follow up beyond 3 years. Given the known reduced comorbidities and no operative risk with radiotherapy the data supports a greater use of radiotherapy in this cohort. Patients across Europe with cN+M0 bladder cancer should be offered both surgery and radiotherapy as treatment options.

Proffered Papers: MR-guided radiotherapy

OC-0419 Patterns of Care and Safety in 1800 patients treated on a high-field MR-Linac platform registry

J. Westerhoff 1 , L. Daamen 1 , J. Christodouleas 2 , E. Blezer 1 , A. Choudhury 3 , R. Westley 4 , B. Erickson 5 , C. Fuller 6 , S. Hafeez 7 , U. van der Heide 8 , M. Intven 9 , A. Kirby 10 , S. Lalondrelle 10 , B. Minsky 6 , S. Mook 11 , M. Nowee 8 , C. Marijnen 8 , K. Orrling 12 , A. Sahgal 13 , C. Schultz 5 , R. Tersteeg 9 , A. Tree 14 , C. Tseng 13 , J. van der Voort van Zyp 9 , H. Verkooijen 15 , W. Hall 5 1 University Medical Center Utrecht, Division of Imaging and Oncology, Utrecht, The Netherlands; 2 Elekta AB, Elekta, Stockholm, Sweden; 3 The University of Manchester and The Christie National Health Service Foundation Trust, Radiation Oncology, Manchester, United Kingdom; 4 The Royal Marsden NHS Foundation Trust, Radiation Oncology, London, United Kingdom; 5 Medical College of Wisconsin, Department of Radiation Oncology, Milwaukee, Wisconsin, United States Minor Outlying Island; 6 University of Texas MD Anderson Cancer Center Houston, Department of Radiation Oncology, Houston, Texas, United States Minor Outlying Island; 7 The Royal Marsden NHS Foundation Trust, The Institute of Cancer Research, London, United Kingdom; 8 Netherlands Cancer Institute, Department of Radiation Oncology, Amsterdam, The Netherlands; 9 University Medical Center Utrecht, Department of Radiation Oncology, Utrecht, The Netherlands; 10 The Royal Marsden NHS Foundation Trust and The Institute of Cancer, Radiation Oncology, London, United Kingdom; 11 University Medical Center, Department of Radiation Oncology, Utrecht, The Netherlands; 12 Lygature, ., Amsterdam, The Netherlands; 13 Sunnybrook Health Sciences Centre-Odette Cancer Centre, Department of Radiation Oncology, Toronto, Canada; 14 The Royal Marsden NHS Foundation Trust and The Institute of Cancer, Department of Radiation Oncology, London, United Kingdom; 15 University Medical Center Utrecht, Department of Imaging and Oncology, Utrecht, The Netherlands 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