S100
Brachytherapy - Head & neck, skin, eye
ESTRO 2026
simplified 1D model assuming central placement. Results: For the CCB plaque, displacement led to a symmetric increase in treatment time, with the optimal position at the tumor apex. In contrast, the CIB and COB plaques showed minimum treatment times when placed eccentrically. The largest effect was observed with the CIB plaque in thinner tumors, where eccentric placement reduced treatment time by up to 8.8% (Figure 2).
Digital Poster 1350 Impact of Ruthenium-106 plaque displacement in ocular interventional radiotherapy (modern brachytherapy) Elisa Placidi 1 , Enrico Rosa 1,2 , Sofia Raponi 1,3 , Bruno Fionda 1 , Monica Maria Pagliara 4 , Antonio Napolitano 5 , Francesca Greco 1 , Maria Vaccaro 1 , Maria Antonietta Gambacorta 1,6 , Luca Tagliaferri 1,7 , Marco De Spirito 1,3 1 Dipartimento di Diagnostica per Immagini e Radioterapia Oncologica Dipartimento di Diagnostica per Immagini e Radioterapia Oncologica, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. 2 Department of Theoretical and Applied Sciences, eCampus University, Novedrate, Italy. 3 Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, Rome, Italy. 4 Dipartimento Neuroscienze, Organi di Senso e Torace, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. 5 Medical Physics Unit, Bambino Gesù Children’s Hospital, Rome, Italy. 6 Dipartimento di Scienze Radiologiche di Neuroscienze, Università Cattolica del Sacro Cuore, Rome, Italy. 7 Dipartimento di Scienze Radiologiche di Neuroscienze, Università Cattolica del Sacro Cuore, Rome, Italy Purpose/Objective: Ocular interventional radiotherapy with Ruthenium- 106 plaques is a standard treatment for uveal melanoma. While simplified one-dimensional planning generally assumes central alignment of the plaque with the tumor apex, in clinical practice—particularly with notched plaques— it is often necessary to place the plaque eccentrically. This study evaluates, both in- silico and in clinical plans, how plaque displacement affects treatment time and dose distribution. Material/Methods: First, an in-silico analysis using Plaque Simulator software (v6.9.7, Eye Physics LLC, Los Alamitos, CA) was conducted for three 106Ru plaque models: CCB (unnotched), CIB, and COB (both notched), Figure 1. Plaques were shifted along the scleral surface, and the treatment times needed to deliver 100 Gy to the tumor apex were calculated for tumor thicknesses between 1.5 mm and 6 mm.
In the cohort of 36 patients, the analysis of the percentage difference between the recalculated treatment time assuming a 1D geometry and the clinically delivered treatment time, accounting for the real plaque displacement, revealed significant variability across plaque types. The CIB group showed the largest relative deviation, with a mean difference of 8.2% ± 0.6%, followed by the COB group with 1.6% ± 0.3%. In contrast, the CCB group showed no difference, reflecting the fact that these plaques are typically placed centrally on the tumor, in line with the 1D assumption. Conclusion: Eccentric placement of notched plaques significantly affects dose distribution and treatment duration. Simplified 1D planning can result in under- or over- dosing, particularly in thin tumors. Three-dimensional, patient-specific planning is recommended to optimize treatment accuracy and outcomes in ocular brachytherapy. Keywords: brachytherapy, ocular, Ruthenium-106 plaque Digital Poster Highlight 2197 Interstitial and hybrid interventional radiotherapy for difficult-to-treat head and neck basal cell carcinomas: 2-year outcomes Artur Jan Chyrek 1,2 , Wojciech Maria Burchardt 1,2 , Filip Oskaldowicz 3 , Alina Ś wiat ł owska 3 , Joanna Maksim 4 , Adam Kluska 1 , Adam Chiche ł 1 1 Brachytherapy, Greater Poland Cancer Center, Pozna ń , Poland. 2 Electroradiology, Poznan University of Medical Sciences, Pozna ń , Poland. 3 Faculty of Medicine, Poznan University of Medical Sciences,
Secondly, retrospective data from 36 patients treated in our center were analyzed to compare actual treatment durations with those estimated using a
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