Prevalence and type distribution of human papillomavirus in squamous cell carcinoma and intraepithelial neoplasia of the vulva

In this updated systematic review and meta-analysis, we estimate the pooled prevalence of human papillomavirus (HPV) DNA and HPV type distribution in squamous cell carcinoma of the vulva (vulvar cancer) and vulvar intraepithelial neoplasia (VIN). PubMed, Embase and Cochrane Library databases were used to identify studies published between 1990 and 2015 and using a PCR-based or hybrid capture test to evaluate the presence of HPV DNA in vulvar cancer or VIN. Pooled estimates of the HPV prevalence with corresponding 95% confidence intervals (CI) were calculated based on a random effects model. The I2 statistic was used to describe the amount of heterogeneity. In meta-regression analyses, potential sources of heterogeneity were evaluated. We identified 92 eligible papers, comprising altogether 5,015 cases of vulvar cancer (64 papers) and 2,764 cases of VIN (48 papers). The pooled prevalence of HPV in vulvar cancer was 39.7% (95% CI: 35.1-44.4%). Overall, 76.3% (95% CI: 70.1-82.1%) of VIN lesions tested HPV-positive, while the HPV prevalence in new subcategories of VIN, uVIN and dVIN, was 86.2% (95% CI: 73.5-95.5%) and 2.0% (95% CI: 0-10.0%), respectively. Substantial between-study heterogeneity was observed (vulvar cancer: I2 = 88.4%; VIN: I2 = 90.7%) with the largest variation between geographical regions. Among HPV-positive cases, the predominant high-risk HPV type was HPV16, followed by HPV33 and HPV18. HPV6 was detected as a single infection in a small subset of VIN and vulvar cancer samples. Thus, HPV vaccination targeting these HPV types may prevent a substantial number of vulvar lesions.