RB1 and head and neck squamous cell carcinoma: Therefore, we compared the prognostic relevance of six practically applicable biomarkers for assessing HPV status in 153 HNSCC patients, including HPV-DNA-PCR, HPV-DNA-ISH, immunohistochemical p16-Ki67 dual staining, and the protein expression of p16, CyclinD1, and pRb.