Recurrence patterns identify aggressive form of human papillomavirus-dependent vulvar cancer.

BACKGROUND: Vulvar cancer is rare and, as a result, is understudied. Treatment is predominantly surgery, irrespective of the type of vulvar cancer, and is associated with physical, emotional and sexual complications. A cluster of human papillomavirus (HPV)-dependent vulvar cancer patients was identified in Arnhem Land Northern Territory (NT), Australia, in which young Indigenous women were diagnosed at 70 times the national incidence rate. AIMS: To assess whether women from the Arnhem Land cluster differ from women with vulvar squamous cell carcinoma (VSCC) and vulvar intraepithelial neoplasia (VIN) resident elsewhere in the NT in recurrence after treatment, disease progression and mortality. MATERIALS AND METHODS: A retrospective cohort study of NT-resident women diagnosed with VIN or invasive vulvar cancer (VSCC) between 1 January 1993 and 30 June 2015 was undertaken. Time to recurrence was assessed using cumulative incidence plots and Fine and Gray competing risk regression models. Mean cumulative count was used to estimate the burden of recurrent events. RESULTS: Indigenous women from Arnhem Land experienced more recurrences after treatment than non-Indigenous women, the cancers recurred faster, and Indigenous women have worse survival at five years. CONCLUSIONS: In characterising the epidemiological features of this cluster, we have identified a particularly aggressive form of vulvar cancer. This provides a unique opportunity for elucidating the aetiopathological pathways driving vulvar cancer development that may ultimately lead to preventive and therapeutic targets for this neglected malignancy. Further, these findings have important implications for clinical practice and HPV vaccination policy in the affected population.