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

ABSTRACT

OBJECTIVE: High-risk human papillomaviruses (HPV) are an established cause of oropharyngeal cancer. Their relationship with oral cancer remains unclear with detection ranging from 0% to 100%. HPV DNA detection or evidence of exposure alone is insufficient to conclude causality. This systematic review assesses the extent of bias in studies of HPV detection in cancers of the oral cavity. METHODS: PubMed, Ovid MEDLINE, EMBASE, and PsycInfo databases were searched for observational studies reporting the effect of HPV in oral cavity specific cancers. RESULTS: All 15 included studies presented HPV DNA detection or serum HPV-antibodies, none included mRNA E6/E7 analysis. Cases with oral cancer had 5.36 times (95% CI 3.29-8.72) higher odds of having HPV detected compared to controls. The odds of HPV detection were higher in cell-based (OR 6.93; 95% CI 0.82-58.55) and tissue samples (OR 5.28; 95% CI 3.41-8.18) than blood-based samples (OR 3.36; 95% CI 1.53-7.40). CONCLUSION: 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.