S41
Brachytherapy - General brachytherapy
ESTRO 2026
clinically relevant toxicity. These encouraging results support the inclusion of PIRT in the multidisciplinary management of rectal cancer cases at risk for residual disease. Larger prospective studies are needed to confirm these findings and define standardized protocols. Keywords: rectum, interventional radiotherapy, toxicity
Universitario A. Gemelli IRCCS, Rome, Italy. 2 Department of Theoretical and Applied Sciences, eCampus University, Novedrate, Italy. 3 Dipartimento di Scienze Radiologiche, Università Cattolica del Sacro Cuore, Rome, Italy Purpose/Objective: Locally advanced rectal cancer (LARC) remains challenging despite advances in multimodal treatment. When a high risk of microscopically positive resection margins persists after neoadjuvant therapy, a local radiation boost may enhance disease control. Perioperative Interventional Radiotherapy (also known as perioperative modern brachytherapy, PIRT), a form of high-dose-rate (HDR) IRT delivered through catheters placed during surgery, enables precise dose escalation directly to the tumor bed while sparing surrounding tissues. This study reports preliminary clinical outcomes of PIRT as a perioperative boost in We conducted a retrospective analysis of eight patients with LARC who underwent surgery after neoadjuvant external beam radiotherapy to at least 45 Gy, followed by a perioperative HDR PIRT planned on Oncentra Brachy TPS (Elekta) and delivered through interstitial catheters (total dose 12 Gy in four fractions). The primary endpoint was local control; secondary endpoints were treatment-related toxicity and postoperative complications. Local control was analyzed using Kaplan–Meier method. Results: With a median follow-up of 36 months, all eight 8 patients (100%) achieved local tumor control, irrespective of final margin status. No Grade ≥ 3 acute or late toxicities were observed. No postoperative complications attributable to treatment occurred, and hospitalization time was not increased. PIRT was well tolerated and enabled accurate dose delivery to the high-risk surgical bed. patients with LARC. Material/Methods:
Digital Poster 4497 Dosimetric evaluation of the TIMER applicator
using TG-43 and TG-186 formalisms in interventional radiotherapy (modern brachytherapy)
Bruno Fionda 1 , Enrico Rosa 1,2 , Elisa Placidi 1 , Pierpaolo Dragonetti 1 , Valentina Lancellotta 1 , Maria Concetta La Milia 1 , Stefania Manfrida 1 , Filippo Elvino Leone 3 , Alessio Giuseppe Morganti 4 , Gyorgy Kovacs 5 , Marco De Spirito 1,6 , Maria Antonietta Gambacorta 1,3 , Vincenzo Valentini 7 , Luca Tagliaferri 1,3 1 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 Scienze Radiologiche, Università Cattolica del Sacro Cuore, Rome, Italy. 4 Radiation Oncology Department, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy. 5 Gemelli INTERACTS, Università Cattolica del Sacro Cuore, Rome, Italy. 6 Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, Rome, Italy. 7 Centro di Eccellenza Oncologia Radioterapica, Medica e Diagnostica per Immagini, Ospedale Isola Tiberina-Gemelli Isola, Rome, Italy
Purpose/Objective: Interventional radiotherapy (IRT, modern
brachytherapy) for perineal malignancies, including anal canal cancer, is challenged by complex pelvic anatomy and procedural constraints. The TIMER® applicator was developed to address these issues through an adaptable design compatible with multimodal imaging (Figure) (MRI, CT, PET/CT, US) [1]. Material/Methods: An update of the dosimetric validation of the TIMER® applicator was performed: dose distributions for all configurations were calculated using both the TG-43 formalism [2] and the TG-186 algorithm [3] to account for heterogeneities, and comparative analyses were carried out between the two calculation methods. The same clinical target volume (CTV) definition, reconstruction approach, and dwell position activation used in the original validation were applied in this update; dose distributions were evaluated according to the TG-43 and TG-186 formalisms. In particular, CTV
Conclusion: PIRT represents a safe and effective perioperative boost modality in selected patients with LARC. In this preliminary cohort, local control reached 100% with no
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