S660
Clinical – Head & neck
ESTRO 2026
intent underwent weekly CT scans during RT. For each patient, volumes of organs of interest, selected muscles, and body contour were measured on baseline and six weekly scans.Structures of interest included parotid (PG) and submandibular glands (SMG); masticatory muscles (masseter and pterygoid); paravertebral and sternocleidomastoid (SCM) muscles; and body contour at C2 and C4 levels.Weekly volumetric variations and weight loss were recorded and analyzed. Results: Forty-eight patients (36 males, 12 females; mean age 62.5 years, range 36–82) were included. Tumor sites were oropharynx (49%), oral cavity (14%), larynx (12%), hypopharynx (6%), salivary glands (6%), nasopharynx (4%), and occult primary (4%). Half received radical and half adjuvant RT, with or without chemotherapy (77%).Mean volume reduction was 33% for PGs ( − 19.7 ± 11.5 cc) and 30% for SMGs ( − 4.95 ± 3.36 cc). Masticatory and paravertebral + SCM muscles decreased by 15% ( − 1.67 ± 1.27 cc) and 13% ( − 0.67 ± 1.10 cc), respectively. Body contour at C2 and C4 level decreased by 10% and 14%, respectively.The most significant PGs reduction occurred between weeks 3–4 (p < 0.001), 4–5 (p = 0.034), and 5–6 (p = 0.006). SMGs showed a steady decrease from week 2 onward (p < 0.01). Body contour reductions at C2–C4 became significant after week 4 (p < 0.001), while muscular changes remained mild and non-significant.Mean weight loss was 5,9 kg (8% of baseline). Conclusion: Significant volumetric changes in salivary glands and body contour occur from the third week of RT onward. Replanning should therefore be considered starting at week 3 to ensure optimal dose distribution and organ sparing.Additional analysis is currently in progress to assess potential correlations with dosimetric data. Keywords: head and neck, adaptive radiotherapy, replanning Randomized Comparison of Simultaneous Integrated Boost (SIB-IMRT) versus Sequential IMRT in Locally Advanced Head & Neck Cancer Debopam Purakayastha Radiation Oncology, Indira Gandhi Institute of Medical Sciences, Patna, India Purpose/Objective: To compare acute toxicities and 6-month objective response between simultaneous integrated boost IMRT (SIB-IMRT) and sequential (phase-wise) IMRT (SEQ-IMRT) in locally advanced head and neck squamous cell carcinoma (LA-HNSCC). Material/Methods: Digital Poster Highlight 4484
Conclusion: Preservation of non-stimulated saliva production at one-year after definitive (chemo)-RT for HNC is most strongly correlated with dose to SMG, with total volume receiving <40 Gy predictive for a change in MST of <10 ml. This finding provides a novel actionable planning constraint to improve patient outcomes and can be used to inform optimal RT delivery. References: 1. Ringash, J., Warde, P., Lockwood, G., O'Sullivan, B., Waldron, J., & Cummings, B. (2005). Postradiotherapy quality of life for head-and-neck cancer patients is independent of xerostomia. International journal of radiation oncology, biology, physics, 61(5), 1403– 1407. https://doi.org/10.1016/j.ijrobp.2004.08.001 Keywords: Radiation, xerostomia, head and neck cancer Digital Poster 4402 Volumetric Changes During Head and Neck Cancer Radiotherapy: A Single-Center Experience Elena Onorati 1 , Sonia Silipigni 1 , Chiara Demofonti 1 , Gian Marco Petrianni 1 , Roberta Guarnaccia 1 , Edy Ippolito 1,2 , Michele Fiore 1,2 , Sara Ramella 1,2 1 Operative Research Unit of Radiation Oncology, Fondazione Policlinico Universitario Campus Bio- Medico, Rome, Italy. 2 Research Unit of Radiation Oncology, Università Campus Bio-Medico di Roma, Rome, Italy Purpose/Objective: Adaptive radiotherapy (ART) involves acquiring updated images during treatment, modifying the plan accordingly, and using the adapted plan for the remaining fractions. This study aimed to assess weekly anatomical changes in organs of interest, muscles, and body contour during radiotherapy (RT) for head and neck (H&N) cancers, and to identify the optimal timing for replanning. Material/Methods: H&N cancer patients treated with radical or adjuvant
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