ESTRO 2020 Abstract book

S417 ESTRO 2020

accelerator (MR-Linac) based competencies must be developed such that therapeutic radiographers (RTTs) can undertake MRgRT predominantly independently. This work describes the implementation of a protocol-driven ‘clinician-lite’ MRgRT workflow following the identification of MRgRT-based skills and competencies. Material and Methods The implementation of an MRgRT service from the ground- up required the recognition of the new knowledge, skills and competencies needed for safe, efficient MRgRT. To determine the parts of the pathway that could be devolved to RTTs and the skills required to do this, a needs assessment and informal survey of the inter-disciplinary team were undertaken. Competence in these skills was achieved using a mixed-methods educational approach that included tutorials, workshops, focused self-directed reading, and end-to-end workflow testing. The MRgRT pathway was critically evaluated by relevant professionals to encourage multidisciplinary input and discussion, allowing an iterative development of the RTT–led workflow. Starting with the simplest online adaptation strategy ‘adapt-to-position’ (ATP), which consists of a virtual couch shift and online re-planning, clear guidelines were established for the delivery of radical prostate radiotherapy following a ‘clinician-lite’ protocol. Results The enhanced RTT skills identified for MRgRT delivery, developed and practiced throughout the implementation period, included MRI safety and screening, MR image acquisition, MRI-based anatomy, multi-modality image interpretation and registration, and treatment plan evaluation. The roles and responsibilities of the three professional groups (clinicians, RTTs and physicists) and how they have evolved to achieve a ‘clinician-lite’ workflow are in Figure 1. Responsibility for CT-MR registration has been devolved solely to RTTs, and applying a definitive framework identifying agreed threshold and action levels for anticipated treatment scenarios similar to those in CBCT-based image-guided radiotherapy (IGRT), responsibility for approving the new plan has been transferred to physicists and RTTs. To date, a clinician was required for online approval in <4% of fractions. Early indications are that this methodology has the potential to improve patient throughput and improve efficiency (Table 1). This ‘clinician-lite’ approach will be repeated during the establishment of additional clinical sites for ATP MRgRT.

Conclusion A ‘clinician-lite’ MRgRT ATP prostate treatment workflow has been successfully implemented at our institution. Further devolution of roles and responsibilities such as validation of online contouring, planning and plan review competence is in development to enable RTTs to fully lead in the online workflow including in more complex adaptive scenarios. OC-0684 Stereotactic MR-Guided Adaptive Radiation Therapy for Inoperable Pancreatic Cancer C. Hassanzadeh 1 , S. Rudra 1 , L. Henke 1 , H. Kim 1 1 Washington University School of Medicine, Radiation Oncology, St. Louis, USA Purpose or Objective Patients with inoperable pancreatic adenocarcinoma have limited treatment options, with limited durable clinical efficacy of chemoradiation or chemotherapy alone. Stereotactic body radiation therapy (SBRT) to treat pancreatic cancer has been limited by proximity to organs- at-risk (OAR). However, stereotactic magnetic resonance (MR)-guided adaptive radiation therapy (SMART) for such patients has shown promise in safely delivering ablative doses. We sought to demonstrate the benefits of SMART using a 5-fraction approach with daily on-table adaptation. Material and Methods 44 patients with locally advanced, non-metastatic pancreatic adenocarcinoma treated from January 2014- January 2019 underwent SMART at a single institution. Patients were prescribed 50Gy in 5 fractions (BED 100Gy) with a goal 95% PTV coverage by 95% of the prescription subject to hard OAR constraints. Daily online adaptation was performed using MR-guided setup and on-table