In 2017, the American Society of Clinical Oncology (ASCO) published a statement indicating that alcohol is an established and modifiable risk factor for several cancer subtypes.1 The statement is consistent with the classification of alcohol as a carcinogen by the International Agency for Research on Cancer (IARC).

A large meta-analysis of 572 studies that included 486,538 cancer cases demonstrated that heavy drinking increased the risk of oral and pharyngeal, esophageal, colorectal, laryngeal, and breast cancers compared with abstinence or occasional drinking in a dose-dependent manner.2 A positive association between alcohol consumption and cancer risk was also found for stomach, liver, gallbladder, pancreas, lung, melanoma, and prostate cancers.

Several other studies demonstrated that alcohol consumption among cancer survivors was associated with a greater risk of mortality.3,4

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The evidence for the association between alcohol and increased cancer risk is based on epidemiologic studies. The ASCO statement notes that dose-response relationships are important for supporting a causal finding.

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Increased Risk of Cancer

Breast Cancer

A meta-analysis of 26 case-control and cohort studies that included 21,149 breast cancer cases demonstrated that wine consumption increased the risk of breast cancer in a dose-dependent manner.5 The overall relative risk (RR) of breast cancer was 1.36 (95% CI, 1.20-1.54; P < .001) with high vs low wine consumption. The study demonstrated that each 1 g of wine consumed was associated with a 0.59% increase in the risk of developing breast cancer.

Consumption of alcohol after a breast cancer diagnosis was, however, not associated with recurrence or overall survival.6,7 Only daily consumption of more than 20 g of alcohol was associated with breast cancer–related mortality.6

Colorectal Cancer

A meta-analysis of 30 studies that included 26,145 cases of colorectal adenomas demonstrated that every 25 g of alcohol consumed daily conferred a 27% increased risk of adenomas (RR, 1.27; 95% CI, 1.17-1.37).8 This is consistent with another meta-analysis, which included 25 studies, which demonstrated a significantly increased risk of adenomas among individuals who consumed 50 g (RR, 1.16; 95% CI, 1.02-1.33) or 100 g (RR, 1.61; 95% CI, 1.42-1.84) of alcohol daily compared with nondrinkers or occasional drinkers.9

In another meta-analysis, any beer consumption was associated with a significantly increased risk of colorectal cancer (CRC; summary RR, 1.20; 95% CI, 1.06-1.37) compared with non-consumption, particularly among those who drank at least 2 beers per day (summary RR, 1.37; 95% CI, 1.26-1.4).10

Heavy drinking (at least 50 g/day) was associated with CRC-related mortality among males (RR, 1.28; 95% CI, 1.13-1.46), but not females.11