Simulation-free radiotherapy

 

Chairs:

• Marco Fusella
• Lorenzo Placidi

 

Motivation

Simulation-free radiotherapy, often referred to as direct-to-unit (DtU), redesigns the conventional radiotherapy pathway by avoiding or minimizing a dedicated CT simulation appointment and instead leveraging diagnostic imaging combined with rapid, and often adaptive, planning and verification. The topic is timely because simulation-free pathways have already been implemented for selected indications, particularly urgent and palliative treatments, and are increasingly being explored in adaptive and stereotactic workflows. Early experience suggests that visits and time-to-treatment may be reduced without compromising deliverability, provided that appropriate patient selection, image acceptance criteria, and safety checks are in place.

However, DtU should not become merely a vendor-specific feature or a collection of isolated local solutions. Without a shared, user-driven framework, there is a real risk of fragmented implementation, limited transferability across platforms, and insufficient evidence of true clinical and operational value. A vendor-neutral perspective is therefore essential to connect different technological ecosystems, including MR-LINAC, CBCT-guided online adaptive radiotherapy, standard C-arm linacs, proton therapy, and emerging upright or gantry-less concepts. The ambition is to enable centres with very different technological profiles to adopt DtU principles in a way that respects local constraints while maintaining common standards for safety, efficiency, and quality.

This workshop aims to define shared DtU workflow archetypes, minimum technical and safety requirements, and a common framework for evaluating value across centres. A particular focus will be placed on the AI-enabled capabilities required to support direct-to-unit radiotherapy safely and efficiently, including image assessment, segmentation support, synthetic density generation, adaptive decision support, quality assurance assistance, and workflow orchestration. The workshop will also address how these capabilities should be validated, governed, and integrated into clinical practice with appropriate human oversight. The overall goal is to identify where DtU genuinely reduces delays, burden, and cost, where it may instead shift workload, and which next steps are needed for broader multicentre implementation and evidence generation.

Workshop focus

The workshop will address the following key questions:

1. What should count as direct-to-unit radiotherapy?
   Defining the scope of DtU, including what should and should not be considered simulation-free in clinical practice.
2. Which workflow archetypes are most relevant today?
   Comparing DtU approaches across CBCT-oART, MR-LINAC, conventional linacs, proton therapy, and emerging upright or gantry-less platforms.
3. What are the minimum technical and safety requirements?
   Discussing imaging acceptance criteria, electron-density strategies, verification workflows, independent checks, documentation standards, and practical stop rules.
4. Which AI-enabled capabilities are required to support direct-to-unit radiotherapy?
   Identifying the most relevant AI-supported functions across the DtU pathway, including image assessment, auto-segmentation, synthetic image generation, adaptive workflow support, decision support, and QA assistance, while also addressing validation, governance, and human oversight.
5. How should roles, responsibilities, and training be organized?
   Mapping multidisciplinary workflows with explicit attention to RTT task ownership, competency requirements, and escalation rules.
6. How should value be measured across centres?
   Defining a shared KPI framework including time-to-treatment, time-on-unit, staffing effort, rework rate, QA burden, bottlenecks, patient experience, and dosimetric or geometric robustness.
7. What evidence is needed next?
   Identifying the main gaps for multicentre benchmarking, implementation studies, consensus recommendations, and future industry-facing requirements.

Expected outcomes

The expected outcomes of this workshop are:

• a consensus definition and scope for direct-to-unit radiotherapy, including clarification of what should and should not be considered DtU;
• a set of focused workflow archetypes across modalities, including CBCT-oART DtU, MR-LINAC DtU, proton DtU, and upright DtU concepts;
• a cross-modality workflow map describing roles and responsibilities, including RTT task ownership, training needs, and escalation rules;
• a minimum safety and QA framework covering imaging acceptance, electron-density strategy, independent checks, documentation, and stop rules;
• a shared KPI and value framework enabling benchmarking across centres;
• a structured framework describing the AI-enabled capabilities most relevant for safe and scalable DtU implementation, including priorities for validation and clinical governance;
• a prioritized list of future actions, such as an ESTRO-wide survey, a multicentre benchmarking project, a consensus or guidance paper, a practical implementation checklist, and a user-driven vendor requirements list;
• stronger interaction across European centres and potentially a doctoral networks working on DtU-related innovation.

The final outcome will be a user-driven blueprint for DtU implementation, enabling benchmarking across centres and supporting future multicentre studies, surveys, and consensus recommendations.

Workshop format

The workshop will include two preparatory online sessions followed by an on-site meeting. The first online session will provide a common scientific introduction, including an invited lecture on the transition from diagnostic-image-based workflows to direct-to-unit treatment, and will launch topic selection. The second online session will include short participant presentations and finalize the discussion themes. The on-site workshop will combine invited presentations and small-group discussion around 4 to 5 selected topics. A user-driven industry interaction session will allow participants to present jointly defined needs and metrics, with industry responding in terms of feasibility and co-development opportunities rather than product demonstrations.