Heidi S. Rønde is a medical physicist at the Danish Centre for Particle Therapy. She is the co-organiser of an ESTRO pre-meeting bootcamp on reirradiation; a current hot topic across disciplines, as there are many challenges alongside the benefits to retreatment.

12.01.2023

At the next ESTRO conference, reirradiation will be on the agenda for a pre-meeting bootcamp organised by Heidi S. Rønde, Ane Appelt (Leeds, UK) and Eliana Maria Vasquez Osorio (Manchester, UK). It is currently also a prioritised topic in Danish national radiotherapy settings, e.g. at the recent annual meeting of DCCC Radiotherapy.

From the ESTRO course description, it is defined that ‘reirradiation is seeing increasing use in clinical practice, and is becoming part of standard care for many patient groups. However, reirradiation in most clinics is still more art than science.’ The challenges named include: Identifying patients who are candidates for reirradiation, dose constraints for normal tissue, tissue recovery factors, practical clinical workflows, image registration & dose accumulation, treatment planning, etc. Heidi S. Rønde elaborates on the background for the course.

Why do you think it is important to discuss re-irradiation in a European setting?

‘Reirradiation is becoming more important as more patients survive their primary cancers (which is very positive!) with the risk of then getting a recurrence which also needs radiation therapy. There is no common ’standard’ on how to perform re-irradiation. Often it is based on the experience of the individual clinicians and physicists why practice vary considerably across countries and continents.

It is important to improve this field together and share knowledge and evidence to hopefully end up with an evidence based ‘best practice’. Also to enable smaller departments with less resources to perform re-irradiation in the best way possible.’

A newer ESTRO/EORTC publication defining reirradation can be seen here European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus on re-irradiation: definition, reporting, and clinical decision making (The Lancet Oncology, 2022, Oct; 23).

What are the potential gains and downsides of proton therapy for re-irradiation?

‘One of the benefits of proton therapy in the reirradiation setting is the potential to deliver a high(er) dose to the recurrence without increasing the low dose bath to the surrounding tissue. (see also Intensity modulated proton therapy planning study for organ at risk sparing in rectal cancer re-irradiation, Acta Oncologica 2021 Nov;60(11):)

‘The risk of severe toxicity is the limiting factor in reirradiation. The doses to organs at risk are close to the tolerances in the primary course of treatment and the recovery of damage is relatively sparse. Sparing of dose to the organs at risk is therefore essential in reirradiation, even in volumes receiving low and intermediate dose levels. Such sparing may be provided by proton therapy.

Regarding downsides, proton therapy does not reduce the high dose in the near proximity to the target that needs to be taken into account when potential toxicities is evaluated. Metal implants within or close to the tumour makes proton therapy difficult or in some cases impossible. Furthermore, proton therapy is not available for everyone.’

How do you go about recommendations/guidelines for re-irradiation at DCPT?

‘Reirradiation has evolved rapidly at DCPT. We started with the knowledge in house based on former reirradiation trials in the photon clinic and what was associable in the literature.

Last year, I participated in the ESTRO Physics workshop on reirradiation with 25 medical physicists all working with reirradiation. That increased both my own and our departments’ knowledge and we have continued to update our internal guidelines based on the new knowledge. Since the workshop, I have been part of the ESTRO Physics Working Group on Reirradiation – both to increase my own knowledge but also to move this area of expertise forward. This has also resulted in my participation in a series of free webinars on reirradiation and the ESTRO pre-meeting course in Glasgow next year.

At DCPT, we have three reirradiation trials (reirradiation of rectum cancer, anal cancer and head & neck cancer) where we have a ‘standard’ setup. ‘Standard’ in the sense that we have a class solution which we adjust to fit the individual patients as there is no ‘one-size fits all’ in reirradiation. A close collaboration between medical physicist/dose planners and oncologist is needed for reirradiation. We also treat breast cancer patients, where it can be difficult to cover the target due to treatment of the contralateral breast at an earlier stage. Last but not least, we do reirradiation of other diagnoses where it could be beneficial with proton therapy – in these cases, we use our knowledge and setup for our ‘standard’ reirradiation cases and the fact that we have reirradiation experts in our department.’

Read more about the ESTRO pre-meeting courses here: https://www.estro.org/Congresses/ESTRO-2024/ESTRO-2024-Pre-meeting-courses