ESTRO 2025 Congress Report
By the reirradiation focus group (report #4/5)
- Lung cancer reirradiation: optimisation of beam angles with EQD2 integration
Poster Discussion
Presenter: Nathan Torelli
In this dosimetric in-silico study, Nathan Torelli et al. explored whether advanced beam-angle optimisation could reduce toxicity in patients receiving high-dose reirradiation for recurrent non-small cell lung cancer (NSCLC). The study was of 15 complex thoracic cases and used a novel algorithm simultaneously to optimise beam orientation and cumulative equivalent dose in 2Gy fractions (EQD2) dose distribution.
The algorithm aligned dose maps from prior and current treatments, converted them into EQD2, and generated optimised non-coplanar volumetric modulated arc therapy (VMAT) arcs. These were compared with standard coplanar VMAT plans.
Results showed that the use of non-coplanar strategies led to significant dose reductions in critical OARs such as the bronchial tree, oesophagus, and thoracic wall, without compromising target coverage. For example, the bronchial tree saw EQD2 reductions of up to 9.0Gy2, and lung V20Gy2 was reduced on average by 0.7%.
The study demonstrates that automated beam-angle selection using cumulative EQD2 can meaningfully lower OAR doses in complex reirradiation cases and hence support an individualised approach to treatment planning.
- Imaging and image registration
Proffered Papers session
Chairs: Alan McWilliam (UK), Pietro Mancosu (Italy)
Title: Image registration and dose mapping for thoracic reirradiation: pre-trial quality assurance in the Scandinavian CURE Lung trial
Presenter: Hella Sand, Denmark (presentation number: E25-147)
Hella Sand’s presentation was focused on a critical technical prerequisite for safe and effective reirradiation in multicentre settings: the standardisation of methods of both image registration and dose accumulation. The study was conducted as a pre-trial quality assurance (QA) effort for the upcoming CURE lung trial in Scandinavia, a prospective multicentre study on high-dose thoracic reirradiation.
The QA initiative involved six Danish radiotherapy centres, each tasked with performing rigid (RIR) and deformable (DIR) image registration and dose mapping on seven thoracic reirradiation cases. The selected cases represented common clinical scenarios, with anatomical variations that were reflective of real-world complexities. Commercial software platforms used included RayStation, MIM, and Velocity. Each centre was asked to map prior 3D dose distributions onto the new planning CT, then to accumulate dose (in both physical dose and EQD2) using local α/β ratios and, where applicable, dose recovery models. The analysis was focused on OARs, using dose-volume histogram (DVH) bands to evaluate inter-centre variability, particularly in near-maximum doses, which are key endpoints for OAR constraints in the CURE lung protocol.
Significant inter-centre variation was observed in OAR dose estimates, even in cases in which the same image registration techniques were used across centres. While the overall DVH bands showed comparable variation between RIR and DIR, DIR was found consistently to reduce variability in near-maximum doses for most OARs - a critical clinical metric in reirradiation trials. Notably, this benefit of DIR was not statistically significant for the oesophagus and heart, both of which are particularly susceptible to deformation and motion. Based on these findings, the study team recommended DIR over RIR for dose accumulation in the CURE lung trial to improve consistency in cumulative dose estimation. This recommendation is aligned with the trial’s primary endpoint of severe toxicity and underscores the need to minimise uncertainties in high-dose thoracic reirradiation planning.
The CURE lung trial is intended to establish national guidelines for thoracic reirradiation, including clear protocols for treatment planning, dose accumulation, and clinical follow-up. This QA study directly informed the protocol by identifying the most robust and reproducible approach to dose accumulation across centres. Sand’s presentation highlighted that despite the availability of commercial DIR tools, their application in complex anatomical regions such as the thorax is technically demanding. Consistent use of DIR will require further training, QA processes and validation, especially for institutions that participate in multicentre trials or expand their reirradiation services.
Sand’s study made a strong case for the mandatory implementation of DIR in thoracic reirradiation trials and practice. While the use of DIR reduces variability in key dose metrics, the presentation also emphasised that DIR is not a plug-and-play solution; its reliability depends on robust protocols, experienced staff, and anatomical context. This QA effort sets a strong foundation for the CURE lung trial and offers a practical framework for centres that aim to integrate economically sustainable, high-quality reirradiation workflows, reinforcing the critical role of physics-led standardisation in clinical trials and practice.
- Is curatively intended reirradiation in lung cancer patients feasible? A retrospective study with clinical and dosimetric data
Proffered Papers session – Lung 1
Chairs: Lotfi Kochbati (Tunisia), Ursula Nestle (Germany)
Presenter: Marianne Marquard Knap, Denmark (presentation number: E25-2563)
In her presentation, Marianne Marquard Knap provided valuable real-world data on the feasibility and outcomes of curatively intended reirradiation in patients with lung cancer. This retrospective analysis offered a glimpse into clinical practices, toxicity profiles, and survival outcomes among patients who received second courses of thoracic radiotherapy, using advanced dose accumulation techniques.
The study was of patients who had been treated with reirradiation between 2014 and 2019, categorised according to ESTRO-European Organisation for Research and Treatment of Cancer reirradiation types, such as those with overlapping or adjacent volumes from a previous radiotherapy course. Notably, patients were followed through the use of CT imaging every three months for the first two years, then every six months thereafter.
Cumulative dose assessments were conducted using DIR, allowing transfer of the original 3D dose distribution onto the reirradiation CT. Doses were then rescaled into EQD2 to assess cumulative exposure to critical structures.
The patient population was elderly (median age 73 years), with 40% showing poor performance status (PS 2-3). Most had NSCLC, half of them at stage I. The majority (75%) were treated with stereotactic body radiotherapy (SBRT), while the rest received long-course radiotherapy.
The median period between the first and second radiotherapy courses was 21 months. Grade 3 toxicity after the initial course occurred in 12 patients, all of whom recovered. One patient died unexpectedly, possibly related to haemorrhage, although severe comorbidity meant that causality was unclear. One case of grade 4 pneumothorax and pneumomediastinum occurred four years after the radiotherapy, possibly linked to high cumulative dose near the bronchi (Dmax: 76Gy EQD2). Lung toxicity was observed in nine patients, with mean cumulative doses ranging from 6.9Gy to 20.2Gy EQD2. Thoracic wall pain and rib fractures were reported in four patients. Interestingly, high cumulative doses (>250Gy EQD2) did not always correlate with symptoms—31 patients with similar dose levels reported no pain.
In terms of survival, the outcomes were encouraging - median OS for NSCLC patients who were treated with reirradiation using SBRT was 48 months. For patients treated with long-course radiotherapy, median OS was 40 months. In contrast, patients with small cell lung cancer had a median OS of 16 months.
The study supports the feasibility of curative-intent thoracic reirradiation with acceptable toxicity, even in older or comorbid patients. Notably, the use of SBRT reirradiation led to lengthened periods of survival, and this finding reinforces its role in selected cases. Knap highlighted the need for prospective data and referenced the upcoming CURE lung trial,the protocol of which includes dose accumulation, treatment planning, and follow-up standards, with severe toxicity as the primary endpoint. She also addressed the potential role of proton therapy in reirradiation, noting that while it is permitted for selected patients in the CURE lung trial, the decision is currently based on physician discretion, not standardised algorithms. Additionally, the protocol accepts varied fractionation schedules (including SBRT and hypofractionation), hence reflecting real-world practice flexibility.
Don't miss our last report in the reirradiation series, still to come:
• Reirradiation in Evolving Clinical Practice
Dr Gian Marco Petrianni
Operative Research Unit of Radiation Oncology
Fondazione Policlinico Universitario Campus Bio-Medico
Rome, Italy
Member of the ESTRO reirradiation focus group
ESTRO 2025 Social media ambassador for reirradiation
g.petrianni@policlinicocampus.it
LinkedIn: Gian Marco Petrianni
X: Gian Marco Petrianni
Dr Bartek Tomasik
Department of Oncology and Radiotherapy, Faculty of Medicine
Medical University of Gdańsk
Gdańsk, Poland
Member of the ESTRO reirradiation focus group
ESTRO 2025 Social media ambassador for reirradiation
bartlomiej.tomasik@gumed.edu.pl
LinkedIn: Bartłomiej Tomasik
X: https://x.com/B_Tomasik (@B_Tomasik)