Management of head and neck cancer of unknown primary: A phase IV study by DAHANCA

Background: Diagnostic and therapeutic management of patients with head and neck squamous cell carcinoma of unknown primary (HNSCCUP) remains a challenge. The aim of the present phase IV study was to assess adherence to the current Danish guidelines and evaluate the treatment outcome in HNSCCUP patients. Materials and methods: Prospectively collected data in the DAHANCA database from patients treated between 2014 and 2020 was evaluated. The median follow-up was 6.7 years. Treatment included definitive neck dissection (dND), primary (chemo-)radiotherapy ((C-)RT), neck dissection (ND) followed by postoperative (C-)RT (ND + (C-)PORT). Outcome were reported as five-year estimates of loco-regional failure (LRF), ultimate LRF (ULRF), disease specific mortality (DSM), overall survival (OS), and toxicity scores ≥ 3. Results: A total of 288 patients were treated, of which 254 (88 %) received treatment with curative intent and were eligible for adherence assessment. These were allocated to dND (n = 60), (C-)RT (n = 81) and ND + (C-)PORT (n = 113). The HPV/p16 status was known in 95 % of patients with 109 (43 %) positive cases. The 5-year LRF, DSM, and OS for patients treated with curative intent was 22 %, 15 % and 73 %, and in patients with p16 positive disease 16 %, 5 %, and 85 %. The overall guideline adherence was 76 % (192/254). In the adherent group the LRF, ULRF, DSM, and OS were 22 %, 11 %, 16 %, and 73 %, respectively. Conclusion: The study revealed good treatment outcome measures in HNSCCUP patients subject to the Danish guidelines, comparable to other head and neck cancer patients. The observed guideline-deviations did not affect outcome.