Cyclin D1 - A prognostic marker in oropharyngeal squamous cell carcinoma that is tightly associated with high-risk human papillomavirus status

Human papillomavirus-related oropharyngeal squamous cell carcinoma has a unique biology and improved prognosis. A new focus is to identify prognostic biomarkers specifically in this human papillomavirus-positive cohort. We analyzed cyclin D1 immunostaining on a tissue microarray of patients with known clinical follow-up and p16 and human papillomavirus status (by E6/E7 RNA in situ hybridization). Cyclin D1 staining was read visually and digitally. Cutoffs of 5%, 10%, and 30% were separately analyzed as was linear intensity data derived from the image analysis. For the 202 tumors, cyclin D1 expression was > 10% in 25.7% (visual) and 35.5% (digital) of the cases. It was > 30% in 15.8% (visual) and 16.5% (digital) of the cases. High cyclin D1 by both methods, cutoffs, and expression intensity was associated with poorer overall, disease-free, and disease-specific survival in univariate analysis. However, low cyclin D1 expression was also tightly associated with human papillomavirus RNA (P < 1.0 × 10^-18 for all cutoffs) and p16 positivity (P < 1.0 × 10^-14 for all cutoffs). In multivariate analysis using the digital 30% cutoff (the strongest cyclin D1 assessment method), only T stage, p16 status, smoking, and treatment approach associated with survival. Intensity of cyclin D1 expression did, however, significantly substratify the human papillomavirus RNA-positive patients into prognostic subgroups independent of other variables. In summary, cyclin D1 overexpression correlates strongly with patient survival in oropharyngeal squamous cell carcinoma, but its relationship with human papillomavirus status is very tight, and the complex nature of this correlation likely limits any clinical application for cyclin D1 assessment.