ESTRO 2025 - Abstract Book

S982

Clinical – Head & neck

ESTRO 2025

received 45 Gy in 10 fractions of 4.5 Gy using the Simultaneous Integrated Boost (SIB) technique. The average high dose spheres volume was 2.03 cm³ (median 1.91 cm³), and the average CTV volume was 192.52 cm³ (median 171.2 cm³). The mean maximum dose within the spheres was 46.96 Gy (median 46.82 Gy), while the mean dose in the remaining irradiated volume (PTV) was 30.99 Gy (median 30.75 Gy). Results: Treatment was well tolerated, with no severe side effects reported. Mild mucositis (grade 1, per CTCAE v.5) was observed in 10 patients, with the remaining 2 experiencing no mucositis (grade 0). No higher-grade mucositis was noted. Dermatitis was observed as grade 0 in 6 patients and grade 1 in 5 patients, with only one patient experiencing grade 2 dermatitis. Conclusion: SFRT in the palliative treatment of head and neck cancers demonstrated favorable tolerance and an acceptable side effect profile, comparable to traditional palliative radiotherapy. Preliminary findings suggest that SFRT could be a safe and promising palliative treatment option; however, further research is necessary to fully assess its efficacy. Digital Poster Comparative Dosimetric Analysis of Radiotherapy Techniques for Early Vocal Cord Carcinoma: A Single Center Experience Frandeina Pinto G., Uriel A Corro V., Patricia Sarrion R., Mara Garcia L., Francisco J Olloqui U., Alejandra Perez G., Javier Albendea R., Iván Diaz de Cerio, Ana L Rivero P., Ana Reguilon, Marina Gutierrez, Noelia Suarez, Rosa Fabregat, Amaia Ilundain, Paula Delgado, José A Vazquez, Juan I Raba, Rodrigo Astudillo, Enrique Capon, Javier Uzquiza, Maria T Pacheco, Pedro J Prada Radiation Oncology, Hospital Universitario Marqués de Valdecilla, Santander, Spain Purpose/Objective: Radiotherapy is a well-established treatment for early vocal cord cancer, providing excellent tumor control while preserving voice quality. Advanced techniques such as VMAT, helical tomotherapy (HT), and IMRT are widely employed, yet comparative analyses of their dosimetric performance in specific clinical contexts remain limited. This study evaluates their efficacy in target volume coverage (PTV95) and organ-at-risk (OAR) sparing for critical structures, including the spinal cord, submandibular glands, thyroid gland, and carotids. Material/Methods: This single-center retrospective analysis included 18 patients treated between July 2023 and October 2024, all with biopsy-confirmed squamous carcinoma of the early vocal cords. Dosimetric data from VMAT, HT, and IMRT were compared using descriptive statistics and analysis of variance with a p-value threshold of <0.05. Key endpoints included PTV95, spinal cord maximum dose (DMax), and mean doses to the submandibular glands, thyroid, and carotids. Additionally, tumor stage distribution and vocal cord laterality were assessed. Results: VMAT achieved a mean PTV95 of 97.5%, while HT showed a slightly higher mean of 98.25% (p = 0.278). IMRT demonstrated lower coverage with a mean of 96.0% (single-patient data). For spinal cord DMax, VMAT presented a mean maximum dose of 1,956 cGy, slightly higher than HT at 1,857 cGy, and IMRT at 1,390 cGy (p = 0.546). For the submandibular glands, HT had the highest mean doses for both right (574.65 cGy) and left glands (731.13 cGy), followed by VMAT (right: 245.7 cGy, left: 158.53 cGy), and IMRT with the lowest values (right: 24.0 cGy, left: 21.1 cGy; p = 0.076). The thyroid gland received the highest mean dose in HT (1,512.45 cGy), with VMAT and IMRT showing Keywords: SFRT, Spatially Fractionated Radiotherapy 1588