If you had to choose between vices in relation to cancer risk, smoking is by far the worst. It has been difficult to assess the effects of alcohol alone because the major risk seems to be in people who are both heavy drinkers and smokers. This combination is implicated in cancers in the head and neck area—the mouth, throat and oesophagus. Alcohol probably contributes to three in every hundred cancers. It is not certain how alcohol interacts with smoking to increase the risk of these cancers but reducing drinking to a more moderate degree decreases the risk.
It is well known that heavy alcohol drinking causes cirrhosis, or scarring of the liver. This in turn can result in primary cancers of the liver, which are otherwise rare in Western society. Alcohol itself can also increase the incidence of liver cancers.
There is speculation about alcohol drinking and other cancers. Breast cancer may be related to alcohol consumption, but it has been difficult to assess precisely the contribution of alcohol as opposed to other risk factors.