Diagnostic accuracy of FDG-PET/CT in the persistence of lymph node involvement in patients with squamous cell carcinoma of the head and neck treated with radiotherapy, chemoradiotherapy or bioradiotherapy.

INTRODUCTION: The primary objective was to determine the diagnostic accuracy of FDG-PET/CT for identifying persistent cervical lymph node metastases in patients with head and neck squamous cell carcinoma (HNSCC) with clinical nodal involvement (cN+), treated with radiotherapy (RT), chemo-radiotherapy (CRT) or bio-RT, in a cohort with a low prevalence of human papillomavirus (HPV) infection and high exposure to toxic substances.

MATERIALS AND METHODS: This was a retrospective study of 125 patients with cN+ HNSCC treated between 2010 and 2022. All patients achieved complete response of the primary tumour after RT or CRT and had an FDG-PET/CT performed between 2 and 4 months after treatment. Cervical metabolic response was classified as positive, negative, or indeterminate; indeterminate cases were re-evaluated for definitive reclassification.

RESULTS: FDG-PET/CT was initially positive in 10 patients (8.0%), negative in 99 (79.2%), and indeterminate in 16 (12.8%). After review, 12 indeterminate studies were reclassified as positive and 4 as negative. Overall sensitivity was 40.0% and specificity was 94.3%, the positive predictive value (PPV) was 57.1%, and the negative predictive value (NPV) was 89.2%. Among oropharyngeal carcinomas, NPV was 95.8% in HPV-positive tumours and 85.7% in HPV-negative tumours. NPV was higher in patients treated with CRT (92.2%) than in those treated with RT/bio-RT (76.2%).

CONCLUSION: FDG-PET/CT is a useful tool for excluding nodal persistence after RT or CRT in cN+ HNSCC, with a high NPV (89.2%) that supports its value in guiding post-treatment cervical management.