Highlights
- Over 1,300 cancer cases caused by human papillomavirus (HPV) could be prevented annually in Ontario.
- HPV infections are responsible for a substantial proportion of cancers of the cervix, anus, vagina, oropharynx, penis and vulva.
- With the introduction of HPV vaccination through Ontario’s school-based HPV immunization program, the number of new HPV infections occurring in the population is expected to decrease.
In 2013, over 1,300 cancer cases could have been prevented in Ontario if high-risk human papillomavirus (HPV) infections were eradicated in the province. Prevention strategies that have the greatest potential to reduce the number of new cancer cases caused by HPV infection include preventing HPV infections through vaccinations, and stopping the development of associated cervical cancers through screening and appropriate treatment.
Cancers of the cervix, oropharynx and anus account for over three-quarters of the cancers caused by HPV infections (approximately 1,000 new cases). The number of cases of cervical cancer and 7 other cancer types caused by HPV are provided in the figure. In 2013, cervical cancer accounted for the largest number of HPV-associated cancers in Ontario (approximately 500 new cases). Because the presence of HPV infection is necessary for cervical cancer to develop, persistent HPV infection is considered the cause of all cervical cancer cases. In 2013, oropharynx cancer accounted for just over 300 cases and anal cancer accounted for roughly 200 newly diagnosed cancers in Ontario. HPV infections also accounted for a substantial proportion (roughly 50% or greater) of penile, vulvar and vaginal cancers diagnosed in Ontario (approximately 270 new cases combined).
There are over 100 types of HPV that infect the genital tract in men and women. High-risk types of HPV, such as HPV 16 and HPV 18, are associated with over 70% percent of cervical cancers.[1] Cancer screening can identify women with HPV changes in the cervix that could lead to cervical cancer. When these changes are identified, cervical cancer can be avoided by relatively simple and highly effective treatment. In 2013, 3,349 screen-eligible women with a high-grade abnormal Pap test result[2] (indicating more serious changes in the cervical cells that can lead to cancer if not treated) were referred to a specialist or received treatment within 6 months of their screening date.[3] There is strong evidence that HPV 16 and 18 are also associated with cancers of the penis, anus, vulva, vagina, oropharynx and oral cavity.[4][5][6] While most HPV infections do not cause symptoms and can go away spontaneously within 1 to 2 years without causing further harm, some infections persist.[7] Persistent infection with high-risk HPV types can lead to cell changes that may cause cancer.
Although cervical cancer cannot develop without a persistent high-risk HPV infection[8] not all high-risk HPV infections will result in cervical cancer.[9] Factors that determine what makes HPV infections persist or go away are not well understood. The risk of getting cancer when someone has a persistent infection with a high-risk HPV type is increased by a variety of factors, such as tobacco smoking[7] (can increase the risk of oropharyngeal cancer), a weakened immune system (e.g., transplant recipients and people with HIV), use of oral contraceptives (can increase the risk of cervical cancer) and having multiple sexually transmitted infections at the same time (e.g., Chlamydia trachomatis, herpes simplex virus).[7]
HPV is transmitted by intimate skin-to-skin contact. It is the most common sexually transmitted infection. Without vaccination, most sexually active adults will get an HPV infection at some point in their lives.[7] School-based HPV vaccination programs are the most effective way to decrease the frequency of HPV infections in our population. These programs allow young girls and boys to be vaccinated before they have had the opportunity to contract HPV (i.e., before they become sexually active). Ontario’s school-based HPV vaccination program currently offers Grade 7 students (boys and girls) the 9-valent vaccine, which protects against multiple high-risk and low-risk HPV types.
Before the HPV vaccine was available, the number of new high-risk HPV infections among Ontario females was highest in teens ages 15 to 19.[10] Teens and young adults have the highest number of new cases of anogenital infection, with a slight increase in middle-aged women.[7][11] Older adults may also choose to receive the vaccine, although the likelihood of the vaccine providing protection is lower than when it is administered in the school-based programs. Cervical screening should continue for all women regardless of their vaccination status.
As a result of Ontario’s school-based HPV immunization program – which began in the 2007/08 school year – the number of new high-risk HPV infections (primarily types 16 and 18) occurring in the population is expected to decrease. A decreasing trend in HPV infections has already been observed in Ontario and in other regions with more long-standing HPV immunization programs.[12][13][14]
Cancer Care Ontario’s updated screening guidance recommends using the HPV test for cervical screening. Cancer Care Ontario is working with the Ministry of Health and Long-Term Care to implement HPV testing in the Ontario Cervical Screening Program (OCSP). Until then, the OCSP strongly recommends that regular Pap test screening continue. View the Ontario Cervical Screening Guidelines Summary