- After more than 2 decades of decline, the rate of new cases of intra-oral cavity cancers increased from 2003 to 2013.
- The increase in intra-oral cancers has been largely driven by rising rates of oropharyngeal cancer, which is tied to rising rates of human papillomavirus (HPV) infection.
- Ontario’s school-based HPV vaccination program is expected to reduce HPV infection and, in turn, the cancers HPV causes.
After decreasing for over 20 years, the incidence (new cases) rate of intra-oral cancers increased by 3.4% per year from 2003 to 2013. Intra-oral cancers are a subset of oral cavity and pharynx cancers and include cancers of the tongue, mouth and oropharynx. Until 2003, the rate of these cancers had been decreasing by 0.6% per year (all changes statistically significant).
The incidence of oral cavity and pharynx cancers also increased from 2003 to 2013, but the rate of increase for intra-oral cancers was almost twice as high. The increase in intra-oral cancers was greater in males (whose rate increased by 3.8% per year) than females (whose rate increased by 2.6% per year).
The major risk factors for intra-oral cancers are tobacco and alcohol use. Human papillomavirus (HPV) is also a major risk factor for oropharyngeal cancer, but not the other types of intra-oral cavity cancers. While the decrease in intra-oral cancers from 1981 to 2003 was likely driven by a decrease in tobacco use, the increase since 2003 appears to be a result of rising rates of HPV infection. Oropharyngeal cancer incidence increased at a greater rate than other intra-oral cancers between 2003 and 2013. The rise in HPV infection has been linked to changing patterns in sexual behaviour, particularly an increased number of sexual partners and oral sex.
It usually takes years after being infected with HPV for oropharyngeal cancer to develop, and not all oropharyngeal cancers are caused by HPV. While population-level Ontario data on the incidence of oropharyngeal cancers caused by HPV has only just begun to be collected, research has shown that the incidence of oropharyngeal cancers caused by HPV has increased in Canada since 2000. However, Ontario’s school-based HPV vaccination program is expected to reduce HPV in the population over the coming decades, which will likely reduce the burden of HPV-associated cancers.