Genital warts and risk of cancer: a Danish study of nearly 50 000 patients with genital warts.

BACKGROUND We conducted a large national cohort study to examine the risk of cancer among men and women with genital warts (GW). METHODS By use of the Danish National Patient Register, we identified 16,155 men and 32,933 women who received a diagnosis of GW during 1978-2008. Standardized incidence ratios (SIRs) were computed as estimates of the relative risk of specific cancers or sites. RESULTS A diagnosis of GW was strongly related to anal (SIR for men, 21.5; SIR for women, 7.8), vulvar (SIR, 14.8), vaginal (SIR, 5.9), cervical (SIR, 1.5), penile (SIR, 8.2), and head and neck cancer (SIR, 2.8), including subsites of head and neck cancer with confirmed HPV association (SIR for men, 3.5; SIR for women, 4.8). The risks remained elevated for >10 years following GW diagnosis. In addition, we found moderately increased SIR estimates for nonmelanoma skin cancer, smoking-related cancers, and Hodgkin and non-Hodgkin lymphoma. CONCLUSIONS Individuals with GW have a long-term increased risk of anogenital cancers and head and neck cancers. The elevated risks of nonmelanoma skin cancers might indicate an association with HPV, while excess risks of other cancers could point to differences in other risk factors between individuals with GW and the general population.