In a move that has grabbed attention, the American Society of Clinical Oncology (ASCO), an organization of leading American doctors specializing in cancer treatment, has issued a statement on the ties between alcohol and cancer. In an article published Nov. 7 in the Journal of Clinical Oncology, the group cites evidence of links between drinking alcohol and several forms of cancer, including breast cancer, cancer of the mouth and throat, liver cancer and colorectal cancer.
The article has raised eyebrows, however, by including both heavy drinking and light drinking. It also discounts alcohol's possible benefits in fighting heart disease, diabetes and dementia.
The statement includes no new research; instead the article summarizes past studies and analyses. The authors point to rising drinking rates in America as a reason to speak out. What's more, the ASCO conducted a survey and found that only a third of Americans knew alcohol was a risk factor for some cancers.
"The importance of alcohol drinking as a contributing factor to the overall cancer burden is often underappreciated," reads the statement.
Researchers have repeatedly found an association between alcohol consumption, particularly heavy alcohol consumption, and certain forms of cancer, particularly breast cancer, liver cancer and throat cancer. The World Health Organization (WHO) lists alcohol as a risk factor, underneath smoking, obesity, unhealthy diet and a lack of physical activity. "Tobacco use is the single most important risk factor for cancer and is responsible for approximately 22 percent of cancer-related deaths globally," reads a WHO statement. The ASCO statement says that about 5.5 percent of cancers—and 3.5 percent of cancer-related deaths—could be alcohol-related.
But while research has shown that heavy drinking carries a much higher risk, particularly when combined with smoking, the statement by the ASCO argues that even light drinking can slightly raise a woman's risk of breast cancer and increase a common type of esophageal cancer. Heavy drinkers face much higher risks of mouth and throat cancer, cancer of the voice box, liver cancer and, to a lesser extent, colorectal cancers. The ASCO statement also argues that people often are poor judges of how much they are drinking, so the safest course is to cut back or not drink at all.
How big is the risk?
To back up its conclusion, the group refers to a 2015 meta-analysis published in the British Journal of Cancer. In that analysis, the authors concluded that a woman drinking less than one glass of wine a day faced a 1.04 times higher risk of developing breast cancer than a nondrinker. Moderate consumption, or one drink a day, led to a 1.23 times higher risk, while those who drank more faced a 1.61 times higher risk. Similar numbers are provided for cancers of the mouth, throat, liver, colon and rectum.
But neither the ASCO statement nor the 2015 study include percentages to show people's actual risk of developing one of the cancers, just the relative risk. According to the National Cancer Institute, a 40-year-old woman has an absolute risk of 1.45 percent of developing breast cancer in the next 10 years. The ASCO article argues that if she’s a light drinker, that risk would become 1.51 percent, an absolute risk increase of 0.06 percent. Extrapolating those numbers, if 1,667 women in that age range drank less than seven glasses a week, one additional woman might develop breast cancer.
Numerous studies have shown that people who consume moderate amounts of alcohol, and red wine in particular, enjoy lower rates of cardiovascular disease than non-drinkers. But the authors argue that those results may be tainted by non-drinkers who once drank heavily. That ignores a recent study in the Journal of the American College of Cardiology that looked at lifelong abstainers and former drinkers separately and found that moderate drinkers still enjoyed lower rates of heart disease.
The ASCO statement concludes by calling for more research on alcohol and cancer links, for oncologists to pay more attention to alcohol consumption when treating patients and for several public policy recommendations, such as more counseling for heavy drinkers, limiting the number of retail outlets for alcohol sales and their hours, keeping state-controlled liquor stores under government control, reducing youth exposure to alcohol ads and raising excise taxes on alcohol. "Because alcohol use is quite common, an initiative to address alcohol use (particularly high-risk alcohol use) is a potential preventative strategy to decrease the burden of cancer," they write.