Human papillomavirus and p16 in squamous cell carcinoma and intraepithelial neoplasia of the vagina

We estimated the overall and type-specific prevalence of human papillomavirus (HPV) and p16 overexpression in vaginal cancer and vaginal intraepithelial neoplasia (VaIN). We conducted a systematic search of PubMed, Embase and Cochrane Library to identify studies published between 1986 and 2017 using PCR-based or Hybrid Capture 2 tests to evaluate the presence of HPV DNA and/or using any method to detect p16 overexpression in VaIN, vaginal squamous cell carcinoma (VaSCC), or other types of vaginal cancer. Applying a random effects model, we estimated the pooled prevalence of HPV and p16 overexpression along with 95% confidence intervals (CIs). The I-2 statistic was used to assess heterogeneity. We included 26 studies, reporting HPV prevalence and six studies evaluating p16 overexpression. The pooled HPV prevalences in VaSCC (n = 593) and VaIN (n = 1,374) were 66.7% (95% CI = 54.7-77.8) and 85.2% (95% CI = 78.2-91.0), respectively. Substantial inter-study heterogeneity was observed, and analyses stratified on geographic region, type of tissue, HPV detection method or PCR primer type did not fully explain the observed heterogeneity. The most predominant HPV type among the HPV positive VaSCC and VaIN cases was HPV16, followed by HPV33, and HPV45 (in VaIN) and HPV18, and HPV33 (in VaSCC). In pooled analyses, 89.9% (95% CI = 81.7-94.6) of HPV positive and 38.9% (95% CI = 0.9-90.0) of HPV negative vaginal cancers were positive for p16 overexpression. Our findings suggest that vaccination against HPV might prevent a substantial proportion of vaginal neoplasia and highlight the need for further studies of the possible clinical value of p16 testing in these patients.