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Abstract
Introduction/Background Approximately 25–43% of vulvar squamous cell carcinomas (VSCC) are associated with human papillomavirus (HPV). They occur in younger women, are often of warty and basaloid histology and show a better prognosis than non-HPV cancers. The predominant genotypes are HPV 16, 33 and 18. VSCC incidence rates among women younger than 50–60 years are on the rise, partly explained by increasing exposure to HPV. However, studies on HPV-prevalence in VSCC over time are lacking. Thus, our aim was to compare HPV-prevalence and genotype distribution in Norwegian VSCC cases from 1970–75 and 2000–05 and investigate a possible prognostic role of HPV-infection.
Methodology All cases of VSCC from 1970–75 (N=153) and 2000–05 (N=199) were extracted from the Cancer Registry of Norway (N=352). Formalin-fixed, paraffin-embedded tissue blocks were retrieved and DNA was extracted. For 282 cases, HPV-DNA analysis was successfully performed. All samples were tested for 19 different genotypes, using real-time TaqMan PCR. Overall survival rates were calculated using the Kaplan Meier method. Multivariable Cox regression analysis was performed to estimate hazard ratios adjusted for age at diagnosis, FIGO stage and diagnostic period.
Results The percentage of HPV-positive cases increased significantly from 23.8% in 1970–75 to 35.3% in 2000–05 (p=0.037). The predominant genotypes detected were HPV 16 (73%), 33 (21%) and 18 (6%) in both periods. HPV-status was an independent prognostic factor with HPV-positive tumours being associated with a better prognosis, HR=0.65, 95%CI [0.48; 0.86], p=0.003. However, when adjusted for age at diagnosis, FIGO stage and diagnostic period, only higher FIGO stage remained significantly associated with higher mortality.
Conclusion The percentage of HPV-positive VSCCs has increased from 1970–75 until 2000–05. The predominant genotypes are HPV 16, 33 and 18 and have not changed during the last decades. HPV-positive tumours were associated with better survival.