ESTRO 2025 - Abstract Book

S981

Clinical – Head & neck

ESTRO 2025

Bulky nodal disease and smaller initial parotid glands volume were found to be predictors for parotid glands volume reduction, with thresholds of 15 mm and 44 cc, respectively. Body contour changes at week 4 correlated with advanced N-stage (≥ N3), bulky nodal disease (15mm), initial BMI (> 28 kg/m²), initial mean planned dose to the ipsilateral parotid gland (> 31 Gy) and initial primary tumor Clinical Target Volume (> 93 cc). Fewer changes in air cavities volume were associated with induction chemotherapy compared to concomitant chemoradiotherapy. Two- and five-year locoregional control rates were 95%. Overall survival rates were 100% and 93%, respectively.

Conclusion: Re-planning evaluation for NPC patients is recommended at 3 rd week of treatment.

Patients selection strategy for ART could be based on the following clinical criteria: high N stage, bulky nodal disease >15mm, initial BMI>28 kg/m², mean planned dose to the ipsilateral parotid glands >31 Gy, cumulative parotid glands volume <44 cc, high dose CTV of the primary tumor >93cc, and receiving RT without prior induction chemotherapy. It is important to validate these pre-treatment clinical predictors before clinical use.

Keywords: Nasopharyngeal carcinoma, Adaptive RT, replanning

References: Nuyts S, Bollen H, Ng SP, Corry J, Eisbruch A, Mendenhall WM, Smee R, Strojan P, Ng WT, Ferlito A. Proton Therapy for Squamous Cell Carcinoma of the Head and Neck: Early Clinical Experience and Current Challenges. Cancers (Basel). 2022 May 24;14(11):2587. doi: 10.3390/cancers14112587. PMID: 35681568; PMCID: PMC9179360. Yang H, Hu W, Ding W, Shan G, Wang W, Yu C, Wang B, Shao M, Wang J, Yang W. Changes of the transverse diameter and volume and dosimetry before the 25th fraction during the course of intensity-modulated radiation therapy (IMRT) for patients with nasopharyngeal carcinoma. Med Dosim. 2012 Summer;37(2):225-9. doi: 10.1016/j.meddos.2011.08.003. Epub 2011 Dec 19. PMID: 22189032.

1515

Digital Poster Implementation of Spatially Fractionated Radiotherapy (SFRT) in Palliative Treatment of Advanced Head and Neck Cancers Tomasz Winiecki 1 , Joanna Kaźmierska 1,2 , Anna Bandurska-Luque 1 , Tomasz Bajon 1 1 Radiotherapy Department II, Greater Poland Cancer Centre, Poznan, Poland. 2 Electroradiology Department, University of Medical Sciences, Poznan, Poland Purpose/Objective: Advanced head and neck cancers, particularly in non-operable cases, present a substantial therapeutic challenge. Radiotherapy remains an important palliative treatment, providing effective symptom control. Spatially Fractionated Radiotherapy (SFRT) allows for precise dose escalation in targeted tumor regions, with initial data suggesting favorable tolerance, low toxicity, and a high number of partial or even complete remissions. This study aimed to evaluate the feasibility of SFRT in palliative therapy for patients with head and neck cancers. Material/Methods: This study included 12 patients (4 women, 8 men), aged 50 to 74 years (median age 63). Tumor sites included the oropharynx (4 patients), hypopharynx (3 patients), oral cavity (3 patients), larynx (1 patient), and CUP syndrome (1 patient). A radiotherapy regimen of 30 Gy, divided into 10 fractions of 3 Gy, was administered to both primary tumors and metastatic lymph nodes. For target volumes (CTV) containing tumors of at least 3 cm, between 2 and 8 high-dose spheres (median 5) were delineated. The diameter of the spheres was 10 mm, and a minimum spacing of 20 mm was maintained between sphere centers. Sphere placement was individually planned by a radiation oncologist, considering tumor volume and proximity to critical structures (organs at risk). Each high-dose sphere