Clinical validation of methylation biomarkers for optimal detection of high-grade vulvar intraepithelial neoplasia

The precursor lesions of vulvar squamous cell carcinoma (VSCC) include human papillomavirus (HPV)-associated and HPV-independent squamous neoplasia with a varying cancer risk. Our study aimed to validate the accuracy of previously identified DNA methylation markers for detection of such high-grade vulvar intraepithelial neoplasia (VIN). A large clinical series of 751 vulvar lesions, originally diagnosed as high-grade VIN, were reassessed and categorized into HPV-associated or HPV-independent vulvar disease categories. Together with 113 healthy vulvar controls, all samples were tested for 12 methylation markers with quantitative multiplex methylation-specific PCR (qMSP). Performance of individual markers and selection of an optimal marker panel for detection of high-grade VIN was determined by logistic regression analysis. SST was the best-performing individual marker (AUC 0.90), detecting 80% of high-grade VIN cases, with excellent detection of HPV-independent VIN (95%), known to have the highest cancer risk. Merely 2% of controls tested methylation positive for SST. Selection of a marker panel, including ZNF582, SST and miR124-2, resulted in a comparably high accuracy for detection of high-grade VIN (AUC 0.89). In conclusion, we clinically validated the accuracy of 12 DNA methylation markers for detection of high-grade VIN. SST, as a sole marker or in a panel, provides an optimal diagnostic tool to distinguish high-grade VIN in need of treatment, particularly HPV-independent VIN, from low-grade or reactive vulvar lesions. These findings warrant further prognostic validation of methylation biomarkers for cancer risk stratification of patients with VIN.