The prevalence of human papillomavirus in oropharyngeal cancer in a New Zealand population.

Background: The incidence of oropharyngeal cancer (OPC) in New Zealand (NZ) has more than doubled over the last 14 years with 126 cases in 2010. Overseas studies have shown that human papillomavirus (HPV) plays a significant role in the development of these cancers. However, the role of HPV in OPC and the burden on the NZ health system is unclear.

Aim: The aim of the study was to determine the prevalence and the genotypes of HPV associated with OPC in New Zealand.

Methods: In this study, 621 OPC were identified from cancer registry data from 1996-98, 2003-05, and 2010-12. Biopsies of 267 cases were then retrieved from laboratories throughout New Zealand. p16 immunohistochemistry and a human beta globin PCR were performed on all specimens. HPV genotyping was performed on all beta globin positive specimens using real-time PCR with melt analysis.

Results: Using a p16/PCR algorithm, 77.9% (95% CI: 71.1-83.5%) of cases were attributable to HPV. Of these, 98.5% were HPV 16 positive. There was also one case each of HPV 33 and 35. The percentage of HPV positive cases increased from 61.9% (95% CI: 40.9%- 79.2%) in 1996-98 to 87.5% (95% CI: 79.8%- 92.5%) in 2010-12. Results from the multivariable model, adjusted for sex and ethnicity found statistically significant associations between HPV positivity and timeframe (OR: 5.65, 95% CI: 2.60-12.30, 2010-12 vs 1996-98), and between HPV positivity and patient age (OR: 0.55, 95% CI: 0.33-0.99, ≥61 years vs ≤60 years).

Conclusions: This data is consistent with data from other developed countries showing an increase in cases of HPV positive OPC in New Zealand, and the majority of cases being attributable to HPV 16. These results support the recent inclusion of males into the nationally funded immunization schedule for Gardasil® 9.