ESTRO 2025 - Abstract Book

S948

Clinical – Head & neck

ESTRO 2025

free survival (PFS), radiation-related toxicities, and patient-reported QOL, assessed using the EORTC QLQ-C30 and QLQ-HN35 up to two years.

Results: A total of 39 patients were analyzed, with 32 patients having tumors in the sinonasal cavity and seven in the oral cavity. Eight patients underwent surgery for HNMM before HF-SSPT: four for residual tumors (one microscopic and three macroscopic) and the remaining four for postoperative recurrence. Following HF-SSPT, 19 patients received immune checkpoint inhibitors, seven of whom were treated for disease progression. No patients received concurrent systemic therapy. The median follow-up period was 29 months. The 3-year OS, LC, and PFS rates were 50%, 83%, and 30%, respectively, while the 5-year rates were 38%, 75%, and 20%. Univariate analysis identified a gross tumor volume of ≥20 cm³ as a significant prognostic factor for poorer PFS. Acute radiation-related toxicities included grade 3 mucositis in five patients (13%) and retinal detachment in one patient (3%). Late toxicities included grade 3 mucositis, sinus disorder, osteonecrosis of the jaw (3% each), and ipsilateral blindness (5%). QOL scores were generally well maintained after HF-SSPT. However, clinically meaningful declines were observed in some items immediately after HF-SSPT, such as "pain" and "swallowing," and at 24 months in "role functioning," "cognitive functioning," and "opening mouth." Conclusion: This study demonstrates that HF-SSPT for HNMM provides good local control with acceptable toxicity. Moreover, QOL was generally maintained over a two-year follow-up. However, the occurrence of early out-of-field recurrences and low long-term survival rates highlight the need for combining HF-SSPT with effective systemic therapies. Digital Poster A systematic review and proportional meta-analysis of image-based pattern of loco-regional failure outcomes in head and neck squamous cell carcinoma Morten Horsholt Kristensen 1 , Signe Bergliot Nielsen 2,1 , Anne Ivalu Sander Holm 3 , Christian Rønn Hansen 4,5,6 , Jens Overgaard 1 , Jesper Grau Eriksen 1 1 Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark. 2 Department of Oto Rhino-Laryngology, Head and Neck Surgery, Aarhus University Hospital, Aarhus, Denmark. 3 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 4 Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark. 5 Department of Clinical Research, University of Southern Denmark, Odense, Denmark. 6 Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark Purpose/Objective: The prognosis following loco-regional failure after primary radiotherapy (RT) for head and neck squamous cell carcinoma (HNSCC) is poor. The hypothesis that most failures occur as a consequence of tumor radioresistance, can be evaluated by proxy as the proportion of failures that occur in the high-dose region. Several studies have investigated possible reasons for treatment failure by an image-based pattern of failure analyses (POF), comparing the initial planning CT scan with a scan conducted upon failure. The aim of the present systematic review and meta analysis was to evaluate the proportion of loco-regional failures that occurred in the high-dose region of all analyzed failures. Material/Methods: A systematic database search from 2000 to 2023, was performed for studies including results from image-based loco-regional POF after primary RT for HNSCC. Methods for pattern of failure analyses included volumetric, point of origin or dosimetric analyses between the target volumes from the planning CT and the failure scan (Figure 1). Keywords: mucosal melanoma, proton therapy 923