S562
Clinical – Head & neck
ESTRO 2026
Mini-Oral 1232
volumes agreed upon by at least 3 radiation oncologists were 3.2, 2.1, and 2.9 times larger than the common GTV overlap obtained from all 19 radiation oncologists, for the three patients, respectively. With respect to GTVs delineated on DECT+MRI, GTVs tended to be more consistent without MRI availability (DECT only, Figure 2C) compared to exchanging DECT with SECT (SECT+MRI, Figure 2B).
Paradigm shift from bilateral elective nodal irradiation to SPECT/CT-based SNP to guide unilateral irradiation in HNSCC: multicenter prospective study Abrahim Al-Mamgani 1,2 , Ellen Zwijnenburg 3 , Pieter D. de Veij Mestdagh 2,1 , Maarten L. Donswijk 4 , Jimmie Honings 5 , Anne I.J. Arens 6 , Luc Karssemakers 7 , Jeroen Houben 2 , Emilia Owers 4 , Willem H. Schreuder 7,8 , Hans Kaanders 3 1 Radiation Oncology, Amsterdam UMC, Amsterdam, Netherlands. 2 Radiation Oncology, Ducth Cancer Institute, Amsterdam, Netherlands. 3 Radiation Oncology, Radboud UMC, Nijmegen, Netherlands. 4 Nuclear Medicine, Ducth Cancer Institute, Amsterdam, Netherlands. 5 Department of Otorhinolaryngology and Head and Neck Surgery, Radboud UMC, Nijmegen, Netherlands. 6 Nuclear Medicine, Radboud UMC, Amsterdam, Netherlands. 7 Department of Head and Neck Surgery, Ducth Cancer Institute, Amsterdam, Netherlands. 8 Department of Otorhinolaryngology and Head and Neck Surgery, Amsterdam UMC, Amsterdam, Netherlands Purpose/Objective: Bilateral elective nodal irradiation (B-ENI) is the standard-of-care for patients with HNSCC of the oropharynx, larynx and hypopharynx treated with (chemo)radiotherapy. This treatment paradigm was empirically determined >50 years ago and has hardly changed ever since, because of a fear of contralateral regional failure (CRF). The incidence of CRF in patients received B-ENI in historical cohorts is around 2.5% with higher rates of toxicity.We aim to investigate the impact of omitting the contralateral (CL) elective nodal irradiation on the incidence of CRF and toxicity in patients who have indication for B-ENI according to
Conclusion: This proof-of-concept study demonstrated the feasibility of setting up multi-centre delineation workflows and highlighted the importance of thorough multi-centre alignment. A larger-scale study including 15 patients is in preparation. References: A warm thanks to all medical physicists supporting the study: Alessandra Bolsi, Alexandra Moignier, Anne Richter, Charlène Bouyer, Evelien Bogaert, Gary Razinskas, Hella Maria Brøgger Sand, Jaccard Maud,Jessica Miller, Kelvin Ng Wei Siang, Linda Rossi, Marie Fargier- Voiron, Nicolas Perichon, Patricia Cambraia Lopes. Keywords: Dual-energy CT, Multi-center delineation study
current guidelines. Material/Methods:
This multicenter prospective study included 90 patients with T1-4N0-2b HNSCC of the oropharynx (n=74, of them 60 were HPV+), larynx (n=6) and hypopharynx (n=10), not crossing the midline. Three to four hours after peritumoral injection of 99mTc- nanocolloid, SPECT/CT was performed. Patients without CL-drainage received unilateral ENI (U-ENI). Patients with CL-drainage underwent surgical sentinel node procedure (SNP) on the same day. If there was no metastasis at the SLN, patients were also treated with U-ENI while patients with CL metastasis were irradiated bilaterally. Results: Of all patients, 82 (91%) received U-ENI only, either because of the absence of CL-drainage (n=49) or because of negative SLN(s) (n=33). Only 8 patients (9%) had positive SLN at the CL neck and received B-ENI.
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