Investigations for Suspected Head and Neck Squamous Cell Carcinoma of Unknown Primary (HNSCCUP): A National Cohort Study.

ObjectivesHead and neck squamous cell carcinoma from unknown primary (HNSCCUP) is a rare and challenging condition. This study aimed to investigate the diagnostic pathways of suspected HNSCCUP patients in the United Kingdom.MethodsA retrospective observational cohort study was conducted, over 5 years from January 2015, in UK Head and Neck centres of consecutive adults undergoing 18F-Fluorodeoxyglucose-PET-CT (PET-CT) within 3 months of diagnosis with metastatic cervical squamous cell carcinoma. Patients with no primary site on examination and no previous head and neck cancer were eligible.ResultsData for 965 patients were received from 57 centres; 68.5% were HPV-related disease. Three investigation cycles were observed: ultrasound with biopsy, cross-sectional imaging (MRI and/or CT) and PET-CT, at median times of 17, 29.5 and 46 days from referral. No primary was identified on PET-CT in 49.8% (n = 478/960). Diagnostic tonsillectomy was performed in 58.2% (n = 278/478) and tongue base mucosectomy (TBM) in 21.7% (n = 104/479). Ipsilateral tonsillectomy carried the highest diagnostic yield (18.7%, n = 52/278), followed by TBM (15.4%, n = 16/104). Contralateral tonsillectomy, performed in 49.0% (n = 234/478), carried the lowest yield (0.9%, n = 2/234). PET-CT with concurrent MRI was associated with higher primary site detection than PET-CT with concurrent CT (p = 0.003). A minority of patients undergoing treatment with curative intent received first-definitive-treatment within 62 days of referral (15.2%, n = 77/505, median 92 days, IQR: 71-117).ConclusionsMost patients experienced a protracted diagnostic pathway and waited over 3 months for definitive treatment. Earlier PET-CT with concurrent MRI may expedite diagnosis. TBM appears more productive than contralateral tonsillectomy for primary site detection.