Vulvar cancer in Germany: increase in incidence and change in tumour biological characteristics from 1974 to 2013

Background: The incidence of vulvar cancer in Germany is increasing. Moreover, gynaecological oncologists reported observing increasing numbers of women presenting with small tumours. The aim of the present study is to validate this observation on a population level and to extend available incidence data.Material and methods: Data from the population-based Saarland Cancer Registry were used and included 1136 women diagnosed with invasive vulvar cancer (ICD-9 codes: 181.1-181.4, ICD-10 code: C51) between 1974 and 2013. Multiple imputation methodology was used to overcome loss of precision and potential bias resulting from incomplete data. Incidence trends were investigated with regard to age at diagnosis, tumour size and clinical stage, morphology and histopathologic grade.Results: The age-standardised incidence rate of vulvar cancer increased from 1.6 cases per 100,000 women per year in 1974-78 to 7.9 in 2009-13, representing an increase across all age groups. Since 1989-93, an almost exclusive increase in the incidence of small tumours 2cm in the greatest dimension from 1.2 to 6.6 and of squamous cell carcinomas from 1.7 to 7.1 was observed, whereas the number of larger tumours and other invasive cancers remained rather constant. Patients aged 75 years generally suffered from more advanced tumours at the time of diagnosis.Conclusions: An increase in vulvar cancer incidence of a size as observed in this study has not been reported thus far for any other European region. Furthermore, the analyses confirmed the observation of increasing numbers of women presenting with small tumours. The results of the age-specific analyses point to both human papillomavirus infection and non-infectious factors as explanations for the observed increase in squamous cell carcinomas.