Updated: May 2003
In British Columbia, incidence of cancers of the head and neck region is 22.9/100,000 in males and 14.9/100,000 in females. Head and neck cancers are a heterogeneous group of tumours, consisting predominantly of squamous cancers of the lip, mouth, pharynx, larynx and cervical esophagus, adenocarcinomas of the major and minor salivary glands and thyroid and occasional tumours of connective tissue origin. Head and neck cancers are more frequent among males than females for most subgroups (ratio ranges from 1.6:1 for the tongue to 3.8 to 1 for the larynx), the only exception being thyroid cancers where the ratio is 0.3 to 1.
Etiological agents vary with the subgroup. Squamous cell carcinomas are most commonly found in those who use tobacco, particularly smokers, and/or those with a high alcohol intake. A synergistic effect is observed when both tobacco and alcohol use are combined. Human papilloma virus is the most likely etiological factor in those who do not use tobacco or drink alcohol.
Nasopharyngeal carcinoma is a tumour of epithelial origin with distinctive epidemiological features. These include a predilection for certain ethnic groups particularly those from Hong Kong and adjacent provinces of southern China, persons from the Middle East and Mediterranean basin and the Inuit. It is strongly associated with exposure to Epstein-Barr virus and some other environmental factors that have not been conclusively identified. There is little or no causal association with tobacco and alcohol consumption in endemic areas.
Some data indicate that various industrial exposures may be related to cancer of the paranasal sinus and nasal cavity.
Exposure to ionising radiation is well known to be associated with an increased risk of thyroid cancer, although most patients with thyroid cancer have no history of radiation exposure. The etiology of most salivary tumours is unknown.
Another indication of the multifactorial nature of cancers in the head and neck region is the possibility that genetic factors may play a role. Such factors might include a variation in the capacity of individuals to metabolize carcinogens (such as those present in tobacco) so that they can be safely excreted from the body. Alternatively, genetically determined variation in efficiency of repair of DNA damaged by carcinogens, might prevent or facilitate mutation to critical genes required for cancer development. This area of research is rapidly developing.
It is well recognised that patients who have had one squamous carcinoma of the upper aero-digestive tract have an increased risk of developing a second primary if the first is cured. The actuarial risk is between 3 and 5% per year. This risk is highest in those who continue to smoke.
