Roles of Ki-67 and p16 as biomarkers for unknown primary head and neck squamous cell carcinoma

PurposeTreatment guidelines have not been established for unknown primary head and neck squamous cell carcinoma (SCC). For these patients, chemoradiotherapy (CRT) can provide a better prognosis than that for patients with other head and neck cancers. The presence of HPV in the tumor is associated with a better outcome. However, not all patients with HPV-positive unknown primary head and neck SCC experience good treatment outcomes in actual clinical settings.MethodsWe thus retrospectively determined the Ki-67 proliferation index and p16 expression status to assess the associations of these parameters with treatment outcomes of patients with unknown primary head and neck SCC.ResultsThe subjects were 13 patients who underwent CRT after surgery or excision biopsy between 1999 and 2016. The 2- and 5-year overall survival (OS) rate was 76.9% and 68.4%, respectively. The prognostic factor was age. There was no significant difference in survival between patients with a high Ki-67 vs. low Ki-67 or between patients with p16-positive vs. p16-negative metastases OS. However, all p16-positive patients with low Ki-67 showed good locoregional control.ConclusionsThe combination of ki67 expression and p16 expression status may allow prediction of local control more accurately than p16 expression status alone.