Human Papillomavirus DNA Methylation Predicts Response to Treatment Using Cidofovir and Imiquimod in Vulval Intraepithelial Neoplasia 3

Response rates to treatment of vulval intraepithelial neoplasia (VIN) with imiquimod and cidofovir are approximately 57% and 61%, respectively. Treatment is associated with significant side effects and, if ineffective, risk of malignant progression. Treatment response is not predicted by clinical factors. Identification of a biomarker that could predict response is an attractive prospect. This work investigated HPV DNA methylation as a potential predictive biomarker in this setting. DNA from 167 cases of VIN 3 from the RT3 VIN clinical trial was assessed. HPV-positive cases were identified using Greiner PapilloCheck and HPV 16 type-specific PCR. HPV DNA methylation status was assessed in three viral regions: and the promoter, using pyrosequencing. Methylation of the HPV region was associated with response to treatment. For cidofovir ( = 30), median methylation was significantly higher in patients who responded ( ≤ 0.0001); methylation >4% predicted response with 88.2% sensitivity and 84.6% specificity. For imiquimod ( = 33), median methylation was lower in patients who responded to treatment ( = 0.03; not significant after Bonferroni correction); methylation