Particle Arc Therapy: from concept to clinical reality


Chairs: Stewart Mac Mein (HIT, Heidelberg, Germany), Xuanfeng Leo Ding (Beaumont, MI, USA)



Particle therapy continues to evolve cancer treatment, promising improved efficacy and efficiency by developing and translating novel treatment and delivery strategies. In particular, clinical interest is growing for dynamic and/or spatially fractionated treatment regimes such as particle arc therapy. Initially, the particle arc concept may seem somewhat counter-intuitive to the main principles of particle therapy, where the conventional particle treatment delivery can be performed with a single or few beams minimizing the patient's integral dose. Additionally, it proposes to utilize a dynamic rotational gantry with hundreds of tons and achieve a submillimeter accuracy, which seems like science fiction. However, with the recent development of novel planning optimization algorithms, new delivery mechanisms, and the compact size proton gantry, such a concept has been demonstrated in a clinical proton system. Recent publications showed improved dosimetric plan quality and more robust and efficient treatment workflows than IMPT in various disease sites and clinical indications.

Indeed, it is technologically and computationally demanding to realize the concept in routine clinical practice. Thus, it is vital for the scientific/clinical community and industry to collaborate and understand how to define clinical drivers for particle arc therapy — for instance, deliverability, efficiency, robustness, radio-biological implications, and clinical role/rationale. Considering these factors, how should we best implement novel techniques like particular arc therapy in the existing and future facilities?

In this workshop, we will discuss the strategies needed for clinical translation in terms of treatment planning, delivery, dosimetry/QA, and radio-biology associated with particle arc therapy.


The outcomes of this workshop are as follows:

  • An international expert group will be established to write a white paper covering the discussed topics and outcomes from the workshop. The white paper will address key issues and challenges identified during the workshop and provide a potential roadmap for clinical translation of particle arc therapy
  • Connecting the international community spanning the academic, clinical and industry space interested in the development and clinical translation of particle arc therapy
  • Report findings and next steps from the workshop at the ESTRO annual meeting in 2023


Invited Speakers

Stefan Both (UMCG, Groningen, Netherlands)

Alejandro Carabe (HUPTI, VA, USA)

Xiaoqiang Li (Beaumont, MI, USA)

Gang Liu (Union Hospital, Wuhan, China)

Konrad Nesgeruk (MGH, MA, USA)

Sophie Wuyckens (UCL, Louvain-la-Neuve, Belgium)

Lewei Zhao (Beaumont, MI, USA)


Participating Vendors

IBA, IBA Dosimetry, Elekta, Leo Cancer Care, RaySearch, etc.


In-person workshop — Preliminary program


Day 1

Friday 7 October


ESTRO physics workshop opening keynote lecture





Introduction and Opening Statement to the Workshop


Session I: Treatment planning (45 min + 75 min discussion)


  • Invited speaker(s):
  • Sophie Wuyckens (dose calculation and optimization algorithms)
  • Lewei Zhao (machine-specific delivery sequence models and clinical applications)
  • RaySearch
  • Elekta





Session II: Treatment delivery, dosimetry & QA (45 min + 75 min discussion)


  • Invited speaker(s):
  • Xiaoqiang Li (current delivery strategies and future directions)
  • Konrad Nesgeruk (gantry-less treatment delivery)
  • IBA, IBA-Dosimetry
  • Leo Cancer Care




Progress report of the different topics



Day 2

Saturday 8 October


Session III: Potential clinical benefits and radio-biological implications

(45 min + 75 min discussion)


  • Invited speaker(s):
  • Stefan Both (clinical experience and model-based patient selection)
  • Alejandro Carabe (treatment planning: RBE & LET considerations)
  • Gang Liu (robustness, motion management, hypofractionation)




Session IV: Break-out groups

  • Group #1: Treatment delivery/QA; Group #2: Treatment Planning/Dosimetry; Group #3: Potential clinical applications
  • 1 page summary (5-10 points) for challenges, solutions and future directions




Session V: Summary and conclusion

  • A representative from each group (Moderators: workshop chairs):
  • Define status, next steps and future collaborations with clinic, academia and industry
  • Brief Discussions:
  • Next steps; take home messages; identify open issues for further research
  • Establish international consortium of experts for white paper


Wrap up: highlights and planned next steps of the different workshops




Online Pre-meeting — Preliminary program


Day 1

September TBD


General Gathering

  • Welcome & housekeeping rules


Introduction to the Workshop and Pre-meeting

  • Workshop Introduction and Outline: main topics, respective goals for in-person meeting
  • Keynote talks: status of the particle arc therapy, key topics/questions of particle arc therapy, open the discussion



  • Introduction of participants and topics


Pitch talks

  • 2 minute presentation (pitch format) from all selected participants
  • Q&A sessions


General Discussion

  • Preparations for the in-person workshop and interactive
  • Participant suggestions and discussion of workshop contents, structure and outcomes
  • Idea collection for workshop: identify issues and brainstorming
  • Establish working groups for in-depth topic elaboration (break-out groups for in-person meeting)



Day 2

September TBD


Select R&D talks + Q&A