9 Human papillomavirus (HPV)

9.1 Virology and the causal link to cancer

Human papillomaviruses (HPVs) are small, non-enveloped DNA viruses from the Papillomavirus family. There are about 150 different HPV serotypes. They vary in their preference for infecting squamous epithelium at different sites, thereby causing the various types of HPV infection (eg, common, palmar, plantar or anogenital). More than 40 HPV types can infect the anogenital tract.1, 2

Data from the US cancer registry3 indicates that HPV is causally associated with almost all cervical cancers, about 69 percent of vulvar, 75 percent of vaginal, 63 percent of penile, 90 percent of anal and 70 percent of oropharyngeal cancers (see Table 9.1).

On the basis of their causal link to cancer, HPVs are divided into low-risk and high-risk types. There are approximately 12 high-risk types, which include 16, 18, 31, 33, 45, 52 and 58. Types 16 and 18 are most frequently associated with cervical cancer but are also causally associated with other cancers. In the US, HPV types 16 and 18 are estimated to cause 66 percent of invasive cervical cancers, 80 percent of anal, 49 percent of vulvar, 55 percent of vaginal, 48 percent of penile and 60 percent of oropharyngeal cancers annually3 (Table 9.1).

Low-risk types are predominantly associated with non-malignant lesions, such as genital warts (especially types 6 and 11), and can also cause recurrent respiratory papillomatosis.

Table 9.1: Average annual percentage of cancer cases attributable to HPV, by anatomic site and sex, United States, 2008–2010

Anatomic site Cancers attributable to any HPVa,b Cancers attributable to
HPV 16, 18a,b
Cancers attributable to HPV 31, 33, 45, 52, 58a,b
% % %
Cervix 90.6c 66.2 14.7
Vulva 68.8 48.6 14.2
Vagina 75.0 55.1 18.3
Penis 63.3 47.9 9.0
female 92.5 79.5 10.8
male 88.7 79.1 3.8
female 63.3 50.8 9.5
male 72.4 63.4 4.4
aData is from 2008–2010 diagnosis years from population-based cancer registries that participate in the National Program of Cancer Registries and/or the Surveillance, Epidemiology, and End Results Program.
bThese estimates do not take into account future changes in incidence, population structure, or the percentage of cancers that are HPV positive.
cAlthough HPV is accepted to be a necessary factor in the causal pathway to invasive cervical cancer, HPV is not always detected in tumour specimens from women who receive a diagnosis of invasive cervical cancer due to a variety of reasons, including misclassification of tissue specimens as cervix, quality of tissue specimens, assay sensitivity, and a small proportion of HPV-negative, cervical cancers.

Adapted from: Saraiya M, Unger ER, Thompson TD, et al. 2015. US Assessment of HPV types in cancers: Implications for current and 9-valent HPV vaccines. Journal of the National Cancer Institute 107(6), Table 4. DOI: 10.1093/jnci/djv086 (accessed 14 September 2016).