The mouth includes the lips, tongue, inside lining of the cheeks, floor of the mouth, gums, palate and salivary glands. Most of the studies identified for the World Cancer Research Fund/Amercian Institute for Cancer Research Third Expert Report Diet, Nutrition, Physical Activity and Cancer: a Global Perspective, did not include cancer of the lips or salivary glands.
The pharynx (or throat) is the muscular cavity leading from the nose and mouth to the larynx, a muscular structure at the upper area of the windpipe, which includes the vocal cords. Cancer of the nasopharynx (the area that connects the back of the nose to the back of the throat) is reviewed separately.
Incidence and survival rates
Taken together, cancers of the mouth (including cancers of the lips and salivary glands), pharynx and larynx (MPL) are the seventh most frequent type of cancer worldwide. Globally, in 2012, an estimated 600,000 new cases were diagnosed, accounting for 4.2 per cent of all new cancer cases. MPL cancers are approximately three times more common in men than in women, which may in part be related to higher rates of smoking in men. Risk increases with age.
The highest rates are found in South-Central Asia, with Bangladesh, India, Pakistan and Sri Lanka contributing more than a quarter of cases in 2012. Globally, 4 per cent of all cancer deaths were attributed to MPL cancers, and they are the seventh most common cause of death from cancer.
Many survivors are left with long-term complications of therapy, related to breathing and food consumption, that require specialised care.
Lifestyle factors and the risk of MPL cancers
In this report from our Continuous Update Project (CUP) – the world’s largest source of scientific research on cancer prevention and survivorship through diet, nutrition and physical activity – we analyse global research on how certain lifestyle factors affect the risk of developing MPL cancers. This webpage forms part of the WCRF/AICR Third Expert Report.
Findings on MPL cancers
There is strong evidence that:
- consuming alcoholic drinks INCREASES the risk of MPL cancers
- being overweight or obese INCREASES the risk of MPL cancers
There is some evidence that:
- consuming non-starchy vegetables might decrease the risk of MPL cancers
- choosing healthy dietary patterns might decrease the risk of MPL cancers
- consuming coffee might decrease the risk of MPL cancers
- consuming mate might increase the risk of MPL cancers
Other causes of MPL cancers
In addition to the findings on diet, nutrition and physical activity outlined above, other established causes of MPL cancers include:
- smoking, chewing tobacco and snuff
Smoking (or the use of smokeless tobacco, sometimes called “chewing tobacco” or “snuff”) is a cause of MPL cancers. Chewing betel quid (nuts wrapped in a betel leaf coated with calcium hydroxide), with or without added tobacco, is also a risk factor for cancers of the mouth and pharynx. It is estimated that as much as 90 per cent of mouth cancers worldwide are attributable to tobacco use, alcohol consumption or a combination of both.
Oral infection with high-risk human papilloma viruses (HPV) is a risk factor for mouth cancer. It is estimated that 72 per cent of oropharyngeal cancer is linked to high-risk HPV infection.
- environmental exposures
Exposure to asbestos increases the risk of laryngeal cancer.
Over 90 per cent of oral cavity, pharyngeal and laryngeal cancers are squamous cell carcinomas.
Cancers of the mouth, pharynx and larynx, like other cancer types, are the result of genetic alterations that lead to small, localised lesions in the mucosal membranes (very thin membranes that cover the gastrointestinal tract from the mouth to the anus) that grow in an abnormal way (dysplasia). These lesions may then progress to carcinoma in situ and/or become invasive cancers.
Exposure to carcinogens can be prolonged and consistent. The mouth and pharynx are directly exposed both to inhaled carcinogens and through eating and drinking. Chronic damage and inflammation caused by stomach acid due to reflux are also implicated. Recent studies have reported that laryngopharyngeal reflux (where stomach acid flows upwards to the larynx and/or pharynx) is associated with laryngeal cancers.
Cancers of the mouth, pharynx and larynx frequently show multiple, independent, malignant foci (location of tumour cells can only be identified microscopically) – with second primary cancers occurring relatively frequently. This phenomenon (referred to as “field cancerisation”) occurs when an entire region of tissue is repeatedly exposed to carcinogens.
Full references and a summary of the mechanisms underpinning all the findings can be found in the MPL cancers report.
How the research was conducted
The global scientific research on diet, nutrition, physical activity and the risk of MPL cancers was systematically gathered and analysed, and then independently assessed by a panel of leading international scientists in order to draw conclusions about which of these factors increase or decrease the risk of developing MPL cancers.
This webpage is a summary.
For much more, download the full chapter.