S596
Clinical – Head & neck
ESTRO 2026
in 56%, and extracapsular spread in 44%. For 87 (42%) of patients, there was no contralateral neck dissection or elective nodal irradiation. Twenty-nine percent received concurrent cisplatin-based chemotherapy (Table).At a median follow-up of 43 months, 3- and 5- year OS were 70% and 55%, respectively. The 3-year cumulative incidence of cancer-related progression was 35%. On multivariable Fine-Grey analysis, extracapsular spread (sHR 1.9, p = 0.01), involved or close margins (sHR 1.7, p = 0.03), and omission of concurrent chemotherapy (sHR 1.6, p = 0.04) were independently associated with increased risk of relapse.Among 87 patients treated with unilateral surgery and RT, 14 (16%) developed locoregional recurrence. Two (2%) occurred at the primary site only, one (1%) involved both the primary and ipsilateral neck, and one (1%) was confined to the ipsilateral neck. Seven (8%) had contralateral neck relapse, including four (5%) with contralateral neck involvement alone (Figure).
This study successfully constructed a radiomics and machine learning-based model for predicting NPC recurrence, confirming that integrating primary tumor and lymph node features significantly enhances predictive performance. Keywords: 5-Year Recurrence,Nasopharyngeal Carcinoma Digital Poster 2465 Patterns of relapse following adjuvant radiotherapy for oral cavity cancer: outcomes of unilateral versus bilateral neck irradiation Joecelyn Kirani Tan 1 , Guy Betts 2 , Zachary Cole-Healey 3 , Kate Garcez 4 , Christopher Hughes 4 , Lip Wai Lee 4 , Sajid Sainuddin 3 , David Thomson 4 , James Price 4 1 Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom. 2 Department of Histopathology, Manchester University NHS Foundation Trust, Manchester, United Kingdom. 3 Department of Oral and Maxillofacial Surgery, Manchester University NHS Foundation Trust, Manchester, United Kingdom. 4 Department of Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom Purpose/Objective: To describe survival outcomes and the pattern of first locoregional failures in patients with resected oral cavity squamous cell carcinoma (OCSCC) treated with adjuvant radiotherapy (RT), with particular focus on the rate of contralateral neck relapse among those managed with unilateral surgery and RT. Material/Methods: Patients with OCSCC who underwent primary surgery followed by adjuvant RT between 2016 and 2020 were identified from institutional treatment records. Demographic, pathological, and treatment variables were collated from a prospectively maintained database. Progression-free survival (PFS) and overall survival (OS) were measured from the date of surgery to the date of first event or last follow-up. Cumulative- incidence functions and Fine-Grey regression were used to explore factors associated with cancer-related progression in the full cohort, treating non-cancer deaths as competing events. For patients treated with unilateral adjuvant RT, sites of first recurrence were categorised as primary only, ipsilateral neck, contralateral neck, or combinations thereof, and summarised descriptively. Results: Two hundred and eight patients were included (median age 64 years, IQR 56-71). Sixty-three percent were male, and 73% had AJCC8 stage IV disease. Margins were <1 mm or involved in 38%, perineural invasion was present in 54%, lymphovascular invasion
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