ESTRO 2024 - Abstract Book

S3504

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

838

Proffered Paper

A multi-institutional overview of clinical re-irradiation dose constraints

Joep Stroom 1 , Myriam Ayadi 2 , Anja Aarberg 3 , Vera Batel 4 , Cemile Ceylan 5,6 , Sinéad Cleary 7 , Lone Hoffmann 8 , Andrew Jackson 9 , Colin Kelly 10 , Charles Mayo 11 , Chrysanthi MichaiIidou 12 , Donna Murrell 13 , Sarah Muscat 14 , Christopher Pagett 15 , Kelly C Paradis 11 , Jaime Perez-Alija 16 , Ellen Yorke 9 , Ali Zaila 17 , Nick West 18 1 Champalimaud Foundation, Radiation Oncology, Lisbon, Portugal. 2 Centre Léon Bérard, Medical Physics, Lyon, France. 3 Haukeland University Hospital, Oncology and Medical Physics, Bergen, Norway. 4 Nordstrahl MVZ GmbH, Medical Physics, Nürnberg, Germany. 5 Istanbul Oncology Hospital, Radiation Oncology, Istanbul, Turkey. 6 University of Yeditepe, Medical Physics, Istanbul, Turkey. 7 Galway University Hospitals, Medical Physics and Bioengineering, Galway, Ireland. 8 Aarhus University Hospital, Oncology, Aarhus, Denmark. 9 MemoriaI Sloan Kettering Cancer Center, Medical Physics, New York, USA. 10 St Luke's Radiation Oncology Network, Medical Physics, Dublin, Ireland. 11 University of Michigan, Radiation Oncology, Ann Arbor, MI, USA. 12 German Oncology Center, Medical Physics, Limassol, Cyprus. 13 London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada. 14 Queen Alexandra Hospital, Medical Physics, Portsmouth, United Kingdom. 15 Leeds Teaching Hospitals NHS Trust, Medical Physics, Leeds, United Kingdom. 16 Hospital de la Santa Creu i Sant Pau, Medical Physics, Barcelona, Spain. 17 King Faisal Specialist Hospital and Research Center, Biomedical Physics Department, Riyadh, Saudi Arabia. 18 Northern Centre for Cancer Care, Medical Physics, Newcastle, United Kingdom

Purpose/Objective:

Since re-irradiation (reRT) of cancer patients is occurring more frequently, ESTRO organized a physics workshop on re-irradiation in October 2022 in Lisbon, PT, which aimed to improve clarity on current reRT procedures and subsequently produce overviews and recommendations. Afterwards, a subgroup of the participants united in order to capture current practice and variations in dose constraints currently being used in the clinical evaluation of patients returning for reRT. This is a necessary step in defining a common language for reRT and ultimately enabling more reliable and consistent constraints in the future. The heterogeneity of published reRT constraints highlights the need for a consistent language to report cumulative doses.

Material/Methods:

Seventeen different centers participated in the study, varying from large university hospitals (>10k treatments/yr) to smaller local centers (~1k treatments/yr). All participants completed a survey regarding their reRT practice (statistics, technique, patient demographics) and cumulative dose constraints. Furthermore, participants filled in a table of reRT dose constraints for 30 different OARs. For reRT patients treated outside of clinical trials, alpha/beta ratios, PRV margins, minimum recovery /intervals, and cumulative constraints in 2Gy-equivalent (EQD2) along with associated references were collected. Although some centers applied different constraints in different clinical situations, only the highest cumulative EQD2 constraint (implying maximum recovery and assuming that maximum allowed dose was delivered in the first course) per OAR and per center will be considered in this abstract. Only Dmax constraints for OARs with data from at least 7 centers will be presented. (Dose-volume constraints were hardly used and removed from this work.) For comparison, an estimated EQD2 Dmax constraint for first-course treatment is shown as well and a relative difference between reRT and first-course constraints is calculated.