Cancer risk associated with alcohol and tobacco use: focus on upper aero-digestive tract and liver.

Alcohol and tobacco, alone or in combination, are associated with an increased risk of various cancers, including those of the upper aero-digestive tract and liver. Both alcohol and tobacco use can increase the risk of cancer of the oral cavity and throat (pharynx), and their combined use has a multiplicative effect on risk. Moreover, those regions of the mouth and pharynx that are more directly exposed to alcohol or tobacco are more likely to be affected by cancer than other regions. A similar effect was found with respect to cancer of the voice box (larynx). For squamous cell carcinoma of the esophagus, alcohol and tobacco also appear to increase risk synergistically. With liver cancer, in contrast, alcohol consumption and tobacco use appear to be independent risk factors. KEY WORDS: Alcohol and tobacco; alcohol consumption; ethanol; smoking; tobacco use; multiple drug use; cancer; risk factors; relative risk; population-attributable risk; oral cancer; pharyngeal cancer; laryngeal cancer; esophageal cancer; liver cancer; hepatocellular carcinoma

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Both alcohol and tobacco use are associated with numerous adverse health consequences, including an increased risk of certain types of cancer. For example, epidemiological studies found that alcohol consumption can increase the risk for cancers of the upper aero-digestive tract, stomach, large bowel (i.e., colon and rectum), liver, and breast, with higher levels of consumption leading to greater increases in risk (Bagnardi et al. 2001). Similarly, tobacco use is associated with an elevated risk of lung cancer, as well as of cancers of the upper aero-digestive tract, bladder, kidney, pancreas, stomach, and cervix and a certain type of leukemia (International Agency for Research on Cancer [IARC] 2004).

Many people use and abuse both alcohol and tobacco, and their combined effects on cancer risk also have been widely investigated. This article summarizes those findings, focusing on cancers at sites that are most directly exposed during alcohol and tobacco consumption--that is, the upper aero-digestive tract (i.e., the oral cavity, throat [pharynx], voice box [larynx], and esophagus) and the liver.

ORAL AND PHARYNGEAL CANCER

In developed countries, oral and pharyngeal cancers rarely occur in people who neither smoke nor drink alcohol. However, many epidemiological studies conducted over the last three decades in the Americas, Europe, and Asia have provided strong evidence of an association between alcohol and tobacco use (both separately and in combination) and an increased risk of oral and pharyngeal tumors (Blot et al. 1988; Franceschi et al. 1990; Zheng et al. 1990, 2004).

Risk Associated With Alcohol Consumption

The risk of both oral and pharyngeal cancer rises steeply with the level of alcohol consumption. An analysis that pooled data (i.e., a meta-analysis) from 26 studies of oral and pharyngeal cancers found that consumption of 25, 50, or 100 g pure alcohol/day (1) was associated with a pooled relative risk (RR) of 1.75, 2.85, and 6.01, respectively, of oral and pharyngeal cancer (see Table 1) (Bagnardi et al. 2001). The RR indicates the strength of the relationship between a variable (e.g., alcohol consumption) and a given disease or type of...