Time trends in prevalence of p16 positivity and combined HPV/p16 positivity in a large cohort of Danish vulvar cancer patients

Vulvar cancer is rare, but causes substantial morbidity in affected patients. A subset of vulvar cancers is caused by high-risk human papillomavirus (hrHPV), which primarily exerts its oncogenic effect through upregulation of tumor suppressor protein p16. Tumors positive for both hrHPV and p16 (double positive) are assumed to be HPV-driven, but only few large studies have investigated the combined prevalence of hrHPV and p16 positivity in vulvar cancer over time. In this Danish cross-sectional study, we assessed the prevalence of p16 positivity and double positivity for hrHPV and p16 in a large sample of vulvar squamous cell carcinomas (VSCCs) diagnosed during 1990 to 2017. In a nationwide register, we identified VSCCs from 13 hospitals across Denmark, and collected archival tumor tissue for hrHPV testing with INNO-LiPA and immunohistochemical p16 staining. We calculated the prevalence of hrHPV, p16 positivity and double positivity according to time, age and histological subtype and evaluated time trends through estimated annual percentage changes. We included 1278 VSCCs. Overall, 35.0% (95% confidence interval [CI]: 32.4-37.6) were positive for p16 and 31.0% (95% CI: 28.4-33.5) were positive for both hrHPV and p16. The prevalence of p16 positivity and double positivity increased over time, both in women aged ≤59 and ≥60 years. The double positive prevalence was higher in nonkeratinizing (60.7%) and warty/basaloid VSCCs (67.5%) than in keratinizing (16.1%) and verrucous VSCCs (5.0%). These results indicate that approximately one-third of vulvar cancers were caused by hrHPV infection, supporting a substantial preventive potential of the HPV vaccine.

Changes in HPV prevalence in Danish women with vulvar cancer during 28 years - A nationwide study of >1300 cancer cases

OBJECTIVE

A substantial proportion of vulvar cancers are caused by high-risk human papillomavirus (hrHPV), but hrHPV prevalence in vulvar cancer has mainly been investigated in smaller studies which did not evaluate time trends. Our aim was to assess hrHPV prevalence in >1300 Danish vulvar cancers diagnosed during 1990-2017, including changes in hrHPV prevalence over time.

METHODS

In a nationwide pathology register, we identified women diagnosed with vulvar cancer at thirteen hospitals from all Danish regions. Archival tumor tissue was collected from local repositories and, upon pathology review, sent to a central laboratory for HPV testing using INNO-LiPA. We calculated hrHPV prevalence according to time, age and histology, and evaluated the overall and age-specific estimated annual percentage change (EAPC).

RESULTS

We included 1308 vulvar cancer cases, with a median age of 72 years at diagnosis. The overall hrHPV prevalence was 52.0% (95% CI: 49.3-54.7). HPV types 16/18 were found in 39.6% of cases, whereas nine-valent HPV (9vHPV) vaccine types 16, 18, 31, 33, 45, 52, and 58 were found in 50.8%. The hrHPV prevalence showed an increasing trend over time, with an EAPC of 0.35% (95% CI: 0.00-0.71). The hrHPV prevalence was higher in younger women throughout the study period, and increasing trends over time were seen in both older (age ≥ 60) and younger (age < 60) women. The hrHPV prevalence was higher in non-keratinizing (71.0%) and warty/basaloid (78.0%) carcinomas than in keratinizing (39.4%) and verrucous (36.4%) carcinomas.

CONCLUSIONS

Our results indicate that the 9vHPV vaccine could potentially prevent a substantial proportion of vulvar cancers in Denmark.