ESTRO 2025 - Abstract Book

S990

Clinical – Head & neck

ESTRO 2025

Purpose/Objective: This study evaluates the impact of treatment de-escalation to 60 Gy, compared to 70 Gy, on patient reported outcomes and toxicity for patients with T1-2 p16-positive oropharyngeal carcinomas treated with primary radiotherapy as part of the ORATOR trials. Material/Methods: Patients with p16-positive squamous cell carcinoma of the oropharynx treated with primary radiotherapy in the ORATOR1 and ORATOR2 randomized trials were included. Patient demographics, tumor and treatment characteristics were compared between patients who received radiation with 70 Gy (ORATOR1, usually with cisplatin every 3 weeks) vs. 60 Gy (ORATOR2, usually with weekly cisplatin). Outcomes examined included quality of life (QOL), toxicity, feeding tube use, overall survival (OS) and progression-free survival (PFS). QOL scores were assessed as changes at 1-year from baseline, using the MD Anderson Dysphagia Inventory (MDADI) and the European Organisation for Research and Treatment of Cancer (EORTC) Core 30 (C-30) and Head-and-Neck 35 (HN-35) scales. Results: The cohort included 59 patients, 29 patients treated with 60 Gy and 30 patients with 70 Gy. There were fewer smokers, both current and previous, in the group treated with 60 Gy (48% [n=14] vs. 80% [n=24], p=0.011). The proportion of patients receiving chemotherapy was similar: 69% [n=20] in the 60 Gy cohort and 77% [n=23] in the 70 Gy cohort (p=0.51). Comparing QOL changes at 1-year in the 60 Gy cohort vs. 70 Gy cohort respectively, the 60 Gy cohort demonstrated improved MDADI total (mean ± SD change +1.9 ± 12.2 vs. -5.8 ± 11.3, p=0.035), and functional (+5.5 ± 12.7 vs. -3.3 ± 12.2, p=0.023) scores. The 60 Gy cohort demonstrated significantly better outcomes at 1-year in several EORTC QOL domains: global health status, fatigue, nausea/vomiting, appetite, constipation, pain, xerostomia, sticky saliva, and coughing (all p < 0.05). For adverse events, patients treated with 60 Gy had significantly lower rates of grade 2-3 dysphagia and grade 2-3 mucositis (all p < 0.05). There was no significant difference in percutaneous feeding tube use at 1-year (n=0 in the 60 Gy cohort vs. n=1 in the 70 Gy cohort). There were no significant differences in OS (5-year 100% in the 60 Gy cohort vs. 93% in the 70 Gy cohort) or PFS (5-year also 100% and 93% respectively). Conclusion: Dose de-escalation from 70 Gy to 60 Gy for p16-positive patients with early-stage squamous cell carcinoma of the oropharynx was associated with better QOL across numerous domains, reduced toxicity, and did not impact OS or PFS in this study.

Keywords: oropharyngeal cancer, quality of life

1671

Mini-Oral Nomogram for estimation of the locoregional control and survival benefit following post-operative radiation therapy for pN0 oral cavity cancer. Max Gau 1 , Jie Su 1 , Shao H Huang 1 , Fatimah A Alfaraj 2 , Robert Oslon 2 , Gustavo N Marta 3 , Luiz P Kowalski 4 , Hugo F Kohler 4 , Leandro L Matos 5 , Fabio Y Moraes 6 , Wei Xu 1 , Enrique Sanz-Garcia 1 , Ezra Hahn 1 , John J Kim 1 , Andrew McPartlin 1 , Brian O’Sullivan 1 , Chiaojung J Tsai 1 , John Waldron 1 , Eitan Prisman 7 , Jonathan C Irish 8 , Christopher MKL Yao 8 , John R de Almeida 8 , David Goldstein 8 , Andrew Hope 1 , Ali Hosni 1 1 Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Canada. 2 Department of Radiation Oncology, BC Cancer, Prince George, Canada. 3 Department of Radiation Oncology, Hospital Sírio-Libanês, São Paulo, Brazil. 4 Department of Head and Neck Surgery and Otorhinolaryngology, A C Camargo Cancer Center, São Paulo, Brazil. 5 Department of Head and Neck Surgery, University of Sao Paulo Medical School, São Paulo, Brazil. 6 Department of Radiation Oncology, Kingston General Hospital, Queen's University,