In situ and invasive squamous cell carcinoma of the vulva in Denmark 1978–2007—a nationwide population-based study

ObjectiveTo determine the incidence of vulvar carcinoma in situ (CIS) and cancer of squamous cell (SC) origin in Denmark in the period 1978–2007.MethodsUsing the nationwide Danish Cancer Registry, we identified 980 women diagnosed with vulvar CIS 1978–2003 (67.8% were SC) and 2455 women diagnosed with vulvar cancer 1978–2007 (76.0% were SC). Analysis was restricted to vulvar CIS and cancer of SC origin. We assessed age-specific incidence rates, age-standardized incidence rates, and distribution of stage at diagnosis. Poisson regression analysis was used to estimate the average annual percentage change.ResultsDuring the study period the age-standardized incidence rate of vulvar SC CIS increased by 1.97% per year (95% CI: 0.99% to 2.96%) with a tendency toward a steeper increase among women younger than 50 years. The age-standardized incidence rate of vulvar SC cancer showed a stable or slightly increasing pattern. However, among women below 60 years of age a significantly increasing trend was observed (1.60% per year; 95% CI: 0.50% to 2.71%). The distribution in the extent of vulvar SC cancer at diagnosis showed a tendency toward a higher proportion being diagnosed with localized disease in the more recent calendar years.ConclusionsThe incidence rates of vulvar SC CIS and vulvar SC cancer among women below the age of 60 years have increased since 1978. Human papillomavirus (HPV) could explain the increase and thus, the recent introduction of HPV vaccination may in the future result in a notable reduction of vulvar malignancies.

Research highlights
► SC vulvar CIS has increased.
► SC vulvar cancer in women ≤ 60 years has increased.
► The proportion of vulvar SC cancer with localized disease tended to increase over time.