Cancers of the upper aerodigestive tract (mouth, pharynx, and larynx). Most UAT cancers are triggered by alcohol and tobacco, which together probably account for three-quarters of cases. Cigarette smoking is associated with increased risk of all of the more common forms of UAT cancer; the risk among cigarette smokers may be 10 or more times that for non-smokers. Pipe or cigar smoking is associated with an even higher excess risk of oral cancer. Chewing tobacco - with or without areca (betel) nut - is strongly linked with oral and pharyngeal cancer, as well as to some extent with cancer of the larynx and the thyroid.
More intense use of tobacco increases risk, while ceasing to smoke for 10 years or more reduces it to virtually equal to that among nonsmokers. The heavier the smoking prior to diagnosis, the more likely people with cancer of the oral cavity, larynx or pharynx are to develop second primaries, i.e. tumours which did not develop from the first one. The same pattern is found among people who continue to smoke after diagnosis.
High alcohol consumption and smoking have synergistic or multiplicative effects on the risk of head and neck cancer. For heavy drinkers who are also heavy smokers, the risk of oral cancer is over 35 times that for those who neither smoke nor drink, and a similar pattern is found with cancer of the larynx. Alcohol consumption is a particularly important risk factor for cancers of the mouth and pharynx, and to a lesser degree, for cancer of the larynx. Consuming 100g of alcohol or more per day (about 12 units - six pints of beer or 12 measures of wine or spirits) multiplies the risk of developing oral cancer at least six-fold, after adjustment for tobacco use; the more alcohol consumed, the greater the risk.
Diet also affects the risk of cancers of the oral cavity, pharynx and larynx; as with many other forms of cancer, frequent consumption of fruit and vegetables is associated with reduced risk. Poor diet is often associated with heavy smoking and alcohol use, and the malnutrition which can result exacerbates the risk of cancer. Eating Cantonese-style salted fish increases risk - which may account for high levels of particular forms of head and neck cancer found among some Chinese ethnic groups.