S665
Clinical – Head & neck
ESTRO 2026
Purpose/Objective: Standard elective nodal irradiation (ENI) for HNSCC recommends doses of 45-60 Gy. These standards evolved before modern imaging and contribute to unnecessary toxicity, as most failures occur in high- dose volumes. Dose de-escalation is an area of active investigation, with emerging data from large academic centers suggesting ENI doses as low as 30 Gy provide excellent control.(MSKCC, Mayo) The purpose of this analysis was to report our outcomes from an experienced MDC community-based US program that prospectively adopted an ENI dose-de-escalation strategy for mucosal HNSCC. Material/Methods: We retrospectively analyzed 100 patients (pts) with HNSCC of the OC, OPX, HPX, LNX, treated with curative intent between May 2017 and May 2025 extracted from our IRB approved RedCap database. Pts received either definitive chemoradiotherapy or postoperative chemo-radiotherapy. Elective nodal volumes (ENV) were uniformly treated to 30-40 Gy, followed by a sequential boost to gross disease or the high-risk surgical bed only. Regions of gross disease received 66-70 Gy or 50-60 Gy after surgery. The primary endpoint was the regional control rate within the elective nodal volume. Secondary endpoints included overall locoregional control and distant metastasis rates. Results: 100 patients with a median age of 65, treated with extreme de-escalated ENI were analyzed. The majority were male (84%). Oropharynx was the most common site (86%), with 84% of tumors testing p16-positive on IHC. Most patients (80%) received definitive chemoradiation, with concurrent cisplatin being the most common systemic therapy (77%). The majority presented with AJCC 8th edition Stage I (48%) or Stage II (25%) disease. Elective nodal volumes were treated to 40 Gy in 81 patients and 30 Gy in 19 patients. With a median follow-up of 25 months, the elective nodal failure rate was 0% agnostic of HPV or stage. The overall recurrence rate was 13% (n=13). All failures occurred outside the low-dose elective nodal volumes and were categorized as distant (n=6), regional (n=4), and local (n=7). Conclusion: To our knowledge, this is the first report of a significant ENI dose-de-escalation strategy for HNSCC being successfully implemented in a community hospital setting, independent of HPV status or surgical intervention. Our findings demonstrate that ENI doses as low as 30-40 Gy are safe and highly effective, yielding excellent elective nodal control when administered with concurrent chemotherapy or Cetuximab. These outcomes align with those from major academic centers, reinforcing that experienced community programs can deliver advanced, evidence-
informed care. These promising results warrant validation in prospective randomized controlled trials. References: 1. Mirghani H, Blanchard P. Treatment de-escalation for HPV-driven oropharyngeal cancer: Where do we stand? Clin Transl Radiat Oncol. 2017 Nov 4;8:4-11. doi: 10.1016/j.ctro.20172. Tsai CJ, McBride SM, Riaz N, et al. Evaluation of Substantial Reduction in Elective Radiotherapy Dose and Field in Patients With Human Papillomavirus–Associated Oropharyngeal Carcinoma Treated With Definitive Chemoradiotherapy. JAMA Oncol. 2022;8(3):364–3723. Ma DJ, Price KA, Moore EJ, et al. Phase II Evaluation of Aggressive Dose De- Escalation for Adjuvant Chemoradiotherapy in Human Papillomavirus-Associated Oropharynx Squamous Cell Carcinoma. J Clin Oncol. 2019 Aug 1;37(22):1909-1918. Keywords: de-escalation, elective neck, 40 Gy Stereotactic Radiotherapy in the Management of Head and Neck Paragangliomas: A Single-Center Study Viola Salvestrini, Isacco Desideri, Carlotta Becherini, Chiara Mattioli, Niccolò Bertini, Marco Banini, Olga Ruggieri, Pierluigi Bonomo, Lorenzo Livi Radiation Oncology Department - Careggi Hospital, University of Florence, Florence, Italy Purpose/Objective: Head and neck paragangliomas (HN-PGs) are rare, slow-growing tumors with a generally favorable prognosis. The management of HN-PGs typically requires a multidisciplinary approach, with radiotherapy playing a key role in achieving durable local control while minimizing toxicity. Stereotactic radiotherapy (SRT) has emerged as a safe and effective modality both as primary and postoperative Digital Poster 4731 treatment. We present our institutional experience with CyberKnife (CK)- and Gamma Knife (GK)-based SRT for patients with HN-PGs. Material/Methods: We retrospectively analyzed consecutive patients who underwent CK- or GK-SRT for HN-PGs between 2016 and 2024 at our center. Collected data included demographics, pre-treatment symptoms, tumor site, prior surgery or radiotherapy, Fisch/Shamblin classification, SRT dosimetric parameters, radiologic response, symptom evolution, and treatment-related adverse events (TRAEs). Toxicities were graded according to CTCAE v5.0. Local control (LC) was defined as the absence of radiologic progression, and survival analyses were performed using the Kaplan– Meier method. Results:
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