Positron emission tomography directed re-irradiation using volumetric modulated arc technique in recurrent head and neck squamous cell carcinoma

Advancements in surgical and radiotherapy techniques have enhanced locoregional control (LRC) in head and neck squamous cell carcinoma (HNSCC), yet 30-40% of patients still experience recurrence within 2-3 years. Salvage surgery can result in significant morbidity and often fails to achieve optimal LRC as a standalone treatment. Modern radiotherapy (RT) techniques support highly conformal re-irradiation for small local recurrences with acceptable toxicity. The role of positron emission tomography (PET-CT) based contouring is under evaluation for re-irradiation settings. This retrospective study included patients treated with re-irradiation at a tertiary care center, focusing on those with prior HNSCC in the oral cavity, pharynx, or larynx, who had received radical or adjuvant RT and presented with biopsy-confirmed recurrences or second primary tumors. PET-CT was used for metastatic workup, with rigid image registration on planning CT scan employing a significant 40% SUVmax cut-off for tumor delineation. From January 2019 to June 2022, 85 patients underwent re-irradiation, with a median RT dose of 60 Gy (range: 44-66 Gy); 32 patients received concurrent chemoradiotherapy (CRT). Treatment planning used the volumetric modulated arc technique (VMAT), with the median Dmax for critical structures ranging from 7 Gy to 63 Gy. Acute grade 3 or higher mucositis, dysphagia, and odynophagia were observed in up to 23.5% of cases. At a median follow-up of 23 months, the 2-year disease-free survival (DFS) and overall survival (OS) rates were 55.2% and 63.5%, respectively. These promising results support PET-CT contouring-based planning as a potential standard of care in re-irradiation.