Assessing bias in the causal role of HPV in oral cancer: A systematic review and meta-analysis.

When cancer site is clearly differentiated between oropharynx and oral cavity, 12 studies showed strong association between HPV and oral cancer, but the available estimates lack internal validity due to inconsistent measurements, high confounding, and lack of gold standard testing. There is not high-quality evidence to conclude a causal relationship of HPV with oral cancer.