Comparative evaluation of dose accumulation strategies in the clinical reirradiation setting

Natasa Solomou; Monica Serban; Piotr Andrzejewski; Nicholas Hardcastle; Lone Hoffmann; Colin Kelly; Chrysanthi Michailidou; Donna H Murrell; Christopher J H Pagett; Marija Popovic; Heidi S Rønde; Nicholas S West; Ali Zaila; Ane L Appelt; Christopher Thompson

doi:10.1016/j.phro.2026.100954

Comparative evaluation of dose accumulation strategies in the clinical reirradiation setting

Phys Imaging Radiat Oncol. 2026 Mar 25:38:100954. doi: 10.1016/j.phro.2026.100954. eCollection 2026 Mar.

Authors

Natasa Solomou¹, Monica Serban^{2

3}, Piotr Andrzejewski⁴, Nicholas Hardcastle^{5

6

7}, Lone Hoffmann^{8

9}, Colin Kelly¹⁰, Chrysanthi Michailidou¹¹, Donna H Murrell¹², Christopher J H Pagett¹³, Marija Popovic¹⁴, Heidi S Rønde¹⁵, Nicholas S West¹⁶, Ali Zaila¹⁷, Ane L Appelt^{13

18}, Christopher Thompson¹³

Affiliations

¹ Department of Radiotherapy Physics, Norfolk and Norwich University Hospitals NHS Foundation Trust, UK.
² Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada.
³ Department of Radiation Oncology, University of Toronto, Toronto, Canada.
⁴ Department of Medical Physics, MedAustron, Vienna, Austria.
⁵ Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia.
⁶ Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia.
⁷ Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
⁸ Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
⁹ Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark.
¹⁰ Department of Medical Physics, St Luke's Radiation Oncology Network, Dublin, Ireland.
¹¹ Department of Medical Physics, German Oncology Center, Limassol, Cyprus.
¹² Verspeeten Family Cancer Centre, London Health Sciences Centre, London, Ontario, Canada.
¹³ Department of Medical Physics, Leeds Teaching Hospitals NHS Trust, Leeds, UK.
¹⁴ Department of Medical Physics, The Ottawa Hospital, Ottawa, Canada.
¹⁵ Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.
¹⁶ Radiotherapy Physics, Northern Centre for Cancer Care, Newcastle upon Tyne, UK.
¹⁷ Biomedical Physics Department, King Faisal Specialist Hospital and Research Center (KFSHRC), Riyadh, Saudi Arabia.
¹⁸ Leeds Institute of Medical Research, University of Leeds, Leeds, UK.

Abstract

Background and purpose: Dose accumulation in reirradiation can contribute to both treatment outcomes and safe cumulative doses. We demonstrated consensus strategies on dose accumulation for three clinical reirradiation scenarios.

Materials and methods: For a lung patient, prescription, point and volumetric-based dose accumulations were generated, while isodose transfer also highlighted a visual approach. In a head and neck case, three-dimensional conformal radiotherapy (3DRT) fields were reconstructed from treatment records. For a brachytherapy gynaecological case, isodose transfer and full volumetric dose accumulation were generated. For pertinent organs at risk (OARs) equieffective doses (EQD2Gy) enabled comparisons between the different methods.

Results: Large variations in cumulative EQD2Gy values in the lung case were calculated. Assuming prescription EQD2Gy, values were 181.9, 161.4 and 154.6 Gy to the spinal canal, brachial plexus and pericardium. Median cumulative point EQD2Gy values for these organs were 15.9, 81.9, 66.6 Gy and similarly, volumetric dose values were 13.9, 68.9 and 55.2 Gy respectively. The head and neck re-simulation showed significant process limitations, especially for brainstem (11.8 - 34.4 Gy EQD2Gy). For the brachytherapy case, cumulative EQD2Gy values were similar across direct point and volumetric dose summation (88.5 vs 88.0 Gy for bladder; 83.6 vs 80.0 Gy for rectum).

Conclusions: Different reirradiation dose accumulation strategies can lead to significant variations in reported OAR cumulative dose. Prescription and point-based dose methods tend to overestimate cumulative dose, which could justify their application in time critical situations, but may limit treatment options. More advanced volumetric-based methods demonstrated improved consistency in cumulative dose reporting.

Keywords: Cumulative dose; Dose accumulation; Dose summation; EQD2Gy; Image registration; Radiotherapy; Reirradiation.