Alcohol And Cancer
"Considerable evidence suggests a connection between heavy alcohol consumption and increased risk for cancer, with an estimated 2 to 4 percent of all cancer cases thought to be caused either directly or indirectly by alcohol" indicates the NIAAA." 3.6% of all cancer cases worldwide are related to alcohol drinking, resulting in 3.5% of all cancer deaths.
Alcohol as a carcinogen and cocarcinogen
The International Agency for Research on Cancer (Centre International de Recherche sur le Cancer) of the World Health Organization has classified alcohol as a Group 1 carcinogen. Its evaluation states, "There is sufficient evidence for the carcinogenicity of alcoholic beverages in humans.… Alcoholic beverages are carcinogenic to humans (Group 1)."
The U.S. National Institute on Alcohol Abuse and Alcoholism (NIAAA) reports that "Although there is no evidence that alcohol itself is a carcinogen, alcohol may act as a cocarcinogen by enhancing the carcinogenic effects of other chemicals. For example, studies indicate that alcohol enhances tobacco's ability to stimulate tumor formation in rats.In humans, the risk for mouth, tracheal, and esophageal cancer is 35 times greater for people who both smoke and drink than for people who neither smoke nor drink, implying a cocarcinogenic interaction between alcohol and tobacco-related carcinogens."
The NIAAA emphasizes that "Although epidemiologic studies have found a clear association between alcohol consumption and development of certain types of cancer, study findings are often inconsistent and may vary by country and by type of cancer."
"Studies have suggested that high concentrations of acetaldehyde, which is produced as the body breaks down ethanol, could damage DNA in healthy cells. … Researchers at the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Maryland, have added weight to this idea by showing that the damage occurs at concentrations of acetaldehyde similar to those in saliva and the gastrointestinal tract while people drink alcohol. Acetaldehyde appears to react with polyamines - naturally occurring compounds essential for cell growth - to create a particularly dangerous type of mutagenic DNA base called a Cr-Pdg adduct…"
Alcohol as risk factor for cancers
This section reviews cancers roughly in the order in which alcohol is believed to increase risk.
Head and neck cancers
Head and neck cancers are a collective term for cancers of the: mouth (oral cavity) esophagus (BE: oesophagus) pharynx larynx
The U.S. National Cancer Institute's (NCI) Cancer Trends Progress Report Alcohol Consumption states that drinking alcohol increases the risk of these cancers in both men and women. In general, these risks increase above the recommended maximum intake (see above). "Heavy alcohol use … leads to greater increases in risk for most of the alcohol-related cancers. … Also, using alcohol with tobacco is riskier than using either one alone, because it further increases the chances of getting cancers of the mouth, throat, and esophagus."
The International Head and Neck Cancer Epidemiology (INHANCE) Consortium co-ordinates research on this topic – see Pooled analysis investigating the effects of beer, wine and liquor consumption on the risk of head and neck cancers.
A study looking at laryngeal cancer and beverage type concluded, "This study thus indicates that in the Italian population characterized by frequent wine consumption, wine is the beverage most strongly related to the risk of laryngeal cancer."
The American Cancer Society estimates that, as a proportion of all cancer deaths in the US in 2006, cancer of the mouth (oral cavity) will represent 1.3 percent, of the esophagus will be 2.4 percent, of the pharynx will constitute slightly under one-half of one percent, and of the larynx will be about six-tenths of one percent.
Although they are also located in the head or neck, alcohol consumption is not a risk factor for brain cancer, eye cancer, pituitary gland cancer, thymus cancer, salivary gland cancer, thyroid cancer, nasal cavity and paranasal sinus cancer, or adenoid cancer. (see below).
Alcohol generally appears to increase the risk of breast cancer in women. The UK's Review of Alcohol: Association with Breast Cancer concludes that "studies confirm previous observations that there appears to be an association between alcohol intake and increased risk of breast cancer in women. On balance, there was a weak association between the amount of alcohol consumed and the relative risk."
The National Institute on Alcohol Abuse and Alcoholism (NIAAA) concludes that "Chronic alcohol consumption has been associated with a small (averaging 10 percent) increase in a woman's risk of breast cancer . According to these studies, the risk appears to increase as the quantity and duration of alcohol consumption increases. Other studies, however, have found no evidence of such a link . "
The Committee on Carcinogenicity of Chemicals in Food, Consumer Products Non-Technical Summary concludes, "The new research estimates that a woman drinking an average of two units of alcohol per day has a lifetime risk of developing breast cancer 8% higher than a woman who drinks an average of one unit of alcohol per day. The risk of breast cancer further increases with each additional drink consumed per day. … The research also concludes that approximately 6% (between 3.2% and 8.8%) of breast cancers reported in the UK each year could be prevented if drinking was reduced to a very low level (i.e. less than 1 unit/week)."
It has been reported that "Two drinks daily increase the risk of getting breast cancer by about 25 percent." (NCI) but the evidence is inconsistent. The Framingham study has carefully track individuals since the 1940s. Data from that research found that drinking alcohol moderately did not increase breast cancer risk. Similarly, research by the Danish National Institute for Public Health found that moderate drinking had virtually no effect on breast cancer risk. Breast cancer constitutes about 7.3% of all cancers. Among women, breast cancer comprises 60% of alcohol-attributable cancers. One study suggests that women who frequently drink red wine may have an increased risk of developing breast cancer.
Alcohol consumption has been shown to increase the rate of breast cancer in women.
"Folate intake counteracts breast cancer risk associated with alcohol consumption" and "women who drink alcohol and have a high folate intake are not at increased risk of cancer". Those who have a high (200 micrograms or more per day) level of folate (folic acid or Vitamin B9) in their diet are not at increased risk of breast cancer compared to those who abstain from alcohol. See Folic acid for more.
Male breast cancer
Heavy alcohol consumption appears to be a low risk factor for male breast cancer, which is a very rare disease.  
The NIAAA reports that "Prolonged, heavy drinking has been associated in many cases with primary liver cancer." However, it is liver cirrhosis, whether caused by alcohol or another factor, that is thought to induce the cancer."
"The chances of getting liver cancer increase markedly with five or more drinks per day" (NCI). However, the risk is cut dramatically by consuming coffee daily. Research has now demonstrated that drinking four cups of coffee per day reduces alcoholic cirrhosis risk by 80% among both men and women of different racial categories (Klatsky et al., Coffee, cirrhosis, and tranaminase enzymes. Archives of Internal Medicine, 2006, 166, 1190-1195).
In areas of Africa and Asia, liver cancer afflicts 50 or more people per 100,000 per year, usually associated with cirrhosis caused by hepatitis viruses. In the United States, liver cancer is relatively uncommon, afflicting approximately 2 people per 100,000, but excessive alcohol consumption is linked to as many as 36% of these cases by some investigators "Mortality rates of hepatocellular carcinoma (HCC) are high in Italy compared with other Western countries. … Overall, 61% of HCC were attributable to HCV [hepatitis C virus], 13% to HBV [hepatitis B virus], and 18% to heavy alcohol drinking." A study in the province of Brescia, northern Italy concluded, "On the basis of population attributable risks (AR), heavy alcohol intake seems to be the single most relevant cause of HCC in this area (AR: 45%), followed by HCV (AR: 36%), and HBV (AR: 22%) infection."
Liver and intrahepatic bile duct cancers combined account for about 2.8% of all cancers.
Colorectal cancer refers to cancers of the colon or rectum. Colorectal cancer constitutes about 9.7% of all cancers.The National Cancer Institute does not list alcohol as a risk factor.
The NIAAA reports that, "Epidemiologic studies have found a small but consistent dose-dependent association between alcohol consumption and colorectal cancereven when controlling for fiber and other dietary factors. Despite the large number of studies, however, causality cannot be determined from the available data."
"Heavy alcohol use may also increase the risk of colorectal cancer" (NCI). One study found that "People who drink more 30 grams of alcohol per day (and especially those who drink more than 45 grams per day) appear to have a slightly higher risk for colorectal cancer." Another found that "The consumption of one or more alcoholic beverages a day at baseline was associated with approximately a 70% greater risk of colon cancer."
One study found that "While there was a more than twofold increased risk of significant colorectal neoplasia in people who drink spirits and beer, people who drank wine had a lower risk. In our sample, people who drank more than eight servings of beer or spirits per week had at least a one in five chance of having significant colorectal neoplasia detected by screening colonoscopy.".
Other research suggests that "to minimize your risk of developing colorectal cancer, it's best to drink in moderation"
Drinking may be a cause of earlier onset of colorectal cancer.
Small intestine cancer
The National Cancer Institute does not list alcohol as a possible risk factor for cancer of the small intestine. 
Leukemia (British spelling: leukaemia). There is no association between drinking alcohol and adult leukemia.
Leukemia in children may be associated with the mother's drinking of alcohol during pregnancy. "Any maternal alcohol use, versus abstinence, during pregnancy was significantly associated with childhood acute lymphoid leukemia (ALL) and acute nonlymphoid leukemia (ANLL) in analyses adjusted for potential confounders." "Three studies have reported an increased risk [of acute myeloid leukemia (AML)] (approximately 1.5-2 fold) in mothers who drank alcoholic beverages during pregnancy. These associations have been particularly apparent in children diagnosed younger than three years of age."
Leukemia constitutes about 7.8% of all cancers.
"Associations were also found between alcohol consumption and cancers of the ovary and prostate, but only for 50 g and 100 g a day." However, one study concludes, "In contrast to the majority of previous studies, we found a positive association between moderate alcohol consumption and the risk of prostate cancer. Liquor, but not wine or beer, consumption was positively associated with prostate cancer."
The Fred Hutchinson Cancer Research Center "found that men who consumed four or more glasses of red wine per week reduced their risk of prostate cancer by 50 percent". They "found no significant effects — positive nor negative — associated with the consumption of beer or hard liquor and no consistent risk reduction with white wine, which suggests that there must be a beneficial compound in red wine that other types of alcohol lack. That compound … may be an antioxidant called resveratrol, which is abundant in the skins of red grapes.".
Prostate cancer accounts for about 4.8% of all cancers.
"Globally, lung cancer is the most frequent malignancy in males, while it is the fifth most common cancer in females."  It is a major cause of death, constituting about 28.8% of all cancers. The NIAA reports that “A few studies have linked chronic heavy drinking with cancers of the stomach, pancreas, and lungs (International Agency for Research on cancer). However, the association is consistently weak and the majority of studies have found no association (International Agency for Research on Cancer).”
Chronic heavy alcohol consumption possibly increases the risk of lung cancer, but the evidence is inadequate to date. Commenting on a study by Freudenheim et al R. Curtis Ellison MD writes, "This study, like others, suggests a weak, positive association between consuming larger amounts of alcohol (>2 drinks a day) and lung cancer risk."
"Associations were also found between alcohol consumption and cancers of the ovary …, but only for 50 g and 100 g a day." "Thus, the results of this study suggest that relatively elevated alcohol intake (of the order of 40 g per day or more) may cause a modest increase of epithelial ovarian cancer risk."
"A few studies have linked chronic heavy drinking with cancers of the stomach, pancreas, and lungs. However, the association is consistently weak and the majority of studies have found no association", write the NIAAA, citing the International Agency for Research on Cancer.. Alcohol has been reported as a possible risks in some (but not in most) studies. Drinking alcohol excessively is a cause of acute pancreatitis and chronic pancreatitis. "About 7 out of 10 cases of chronic pancreatitis are due to long term heavy drinking. Chronic pancreatitis is a known risk factor for cancer of the pancreas. But chronic pancreatitis that is due to alcohol doesn't increase risk as much as other types of chronic pancreatitis. So if there is a link with alcohol and pancreatic cancer risk, it is only very slight."
Pancreatic cancer constitutes about 5.7% of all cancers.
"Thirteen studies to date have reported on the relationship between endometrial cancer and alcohol consumption. Only two of these studies have reported that endometrial cancer incidence is associated with consumption of alcohol; all the others have reported either no definite association, or an inverse association." (Six studies showed an inverse association; that is, drinking was associated with a lower risk of endometrial cancer) "…if such an inverse association exists, it appears to be more pronounced in younger, or premenopausal, women."
Endometrial plus all other uterine cancers account for about 1.9% of all cancers.
As indicated above, the NIAA reports that “A few studies have linked chronic heavy drinking with cancers of the stomach, pancreas, and lungs (International Agency for Research on cancer). However, the association is consistently weak and the majority of studies have found no association (International Agency for Research on Cancer).”
Alcohol consumption, even when chronic and heavy, probably does not affect the risk of stomach cancer.
A review of findings from nine international studies suggests that drinking alcohol reduces the risk of non-Hodgkin’s lymphoma (NHL) by 27%. The protective effect of alcohol did not vary by beverage type. "People who drink alcoholic beverages might have a lower risk of NHL than those who do not, and this risk might vary by NHL subtype. Further study designs are needed to determine whether confounding lifestyle factors or immunomodulatory effects of alcohol explain this association.". The cancer is the sixth most common in the USA.
Kidney cancer (Renal cell carcinoma) (RCC)
Moderate alcohol consumption may reduce the risk of kidney cancer. "Results from our prospective cohort study of middle-aged and elderly women indicate that moderate alcohol consumption may be associated with decreased risk of RCC." Another study concludes, "These findings suggest an inverse association of alcohol consumption and RCC development among women but not among men." However, another study concludes, "No significant relationship emerged, nor any differences between the sexes."
"In interview data from the U.S.A.'s Third National Cancer Survey, alcohol ingestion was associated with a higher occurrence of cancers of the breast, thyroid, and malignant melanoma. Data from other studies support the first two associations." Another study suggests that drinking in moderation significantly reduces the risk of some malignant tumors such as thyroid cancer in women. However, another study concludes, "A reduced risk associated with alcohol was eliminated after adjustment for smoking…".
"In interview data from the U.S.A.'s Third National Cancer Survey, alcohol ingestion was associated with a higher occurrence of cancers of the breast, thyroid, and malignant melanoma. Data from other studies support the first two associations." "High alcohol consumption was associated with an increased risk for melanoma, which remained after adjustment for confounders…". Other studies suggest there is no association for melanoma. "The risk of malignant melanoma was not influenced by alcohol consumption or smoking habits." "There was no evidence that … alcohol or polyunsaturated fats were associated with an increased risk."
There is no association between alcohol and Nonmelanoma skin cancer.
Drinking might be a risk factor for gallbladder cancer.
"Our data suggest that total and beverage-specific alcohol consumption are not associated with an increased risk of bladder cancer." A Dutch study concludes, "The results of this study do not suggest an important association between alcohol consumption and bladder cancer risk." Bladder cancer represents about 2.3% of all cancers.
"No consistent association emerged between milk, meat, liver, alcohol and coffee consumption and risk of vulvar cancer."
For the following cancers, little research has been published, but alcohol is not listed as a risk factor:
Thymus cancer 
Kaposi's sarcoma 
Eye cancer  
Adrenal gland cancer 
Brain cancer 
Cervical cancer 
Adenoid cancer  
Bile duct cancer 
Urethral cancer 
Spinal cancer 
Ewing's family of tumors 
Extragonal germ cell cancer 
Extrahepatic bile duct cancer  \ Fallopian tube cancer 
Soft tissue cancers 
Bone cancer 
Hodgkin's lymphoma 
Anal cancer 
Malignant mesothelioma 
Vaginal cancer 
Skin cancer 
Central nervous system cancer (craniopharyngioma) 
Pleuropulmonary blastoma 
Nasal cavity and paranasal sinus cancer 
Transitional cell cancer of renal pelvis and ureter 
Pituitary gland cancer 
Salivary gland cancer 
Effect of alcohol on the progress of cancer when established
A study of the influence of alcohol intake on tumor growth of hepatocellular carcinoma (HCC) in patients with type C cirrhosis, found that alcohol influenced tumor volume doubling time (TVDT). "In conclusion we found that alcohol intake was closely related to the tumor growth of HCC in patients with type C cirrhosis."
A study of chick embryos suggests that alcohol stimulates their tumor growth by fueling the production of a growth factor that stimulates blood vessel development in tumors. A 2006 study in mice showed moderate drinking resulted in larger and more robust tumors.
A study where high amounts of alcohol were given to mice suggests that it accelerates their cancer growth by speeding up the loss of body fat and depressing immune activity - particularly that of 'killer t-cells'.
Relative health risks
An increase in risk of a particular cancer through drinking needs to balanced against the benefits of moderate drinking on reducing heart attacks. See Alcohol and heart attacks for more. There are, of course, many ways of reducing your risk of a heart attack either without, or in addition to, drinking alcohol, such as controlling your weight and exercising. Balancing such risks is a personal decision that should be discussed with one’s own physician.