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.