Head and neck squamous cell carcinoma of unknown primary treated in the era of FDG-PET and IMRT

Purpose or Objective Head and neck carcinoma of unknown primary (HNCUP) is a diagnosis of exclusion after an extensive workup. Since the introduction of PET-CT in the diagnostic arsenal the area of true unknown primaries narrowed. Most literature available nowadays describes cohorts of patients before the era of PET-CT and IMRT. This cohort thus represents a more applicable patient selection for current medical practice. Material and Methods Retrospective analyses of 80 PET-staged patients that were curatively treated with intensity-modulated radiotherapy (IMRT) between 2006 and 2016. Patient, tumor and treatment demographics were recorded and oncologic outcomes were analyzed. Results Half of the patients underwent upfront neck dissection, mostly (super)selective. Of all, 97% received mucosal irradiation. Unilateral irradiation of the neck was done in 18% of the patients. Overall survival at 5 year was 62% and disease specific survival 78%. Extracapsular extension (ECE), N3 neck, multiple levels of positive lymph nodes (PLN) and PLN in the lower neck were associated with worse prognosis. Local control was 100% in the mucosal irradiated patients. Neck control was 90%. In total 10 patients developed distant metastases, N3, ECE and lower neck PLN were associated with DM. Patients treated unilaterally had significantly less acute dysphagia grade III (0% vs. 33%). Conclusion This series gives a current overview of the HNCUP patients treated over the last 10 years in the Netherlands Cancer Institute by IMRT in the era of FDG-PET. Five-year disease specific survival is fairly good with 78%, however ECE, N3 and lower neck PLN are factors associated with a worse prognosis. These patients are prone for distant metastasis and future research need to focus on identification of these patients and development of new strategies to improve the outcome of this group of patients.