, by NCI Staff
Nearly 750,000 cases of cancer diagnosed worldwide in 2020, or 4%, can be attributed to alcohol consumption, according to a new study from the World Health Organization (WHO). While heavy drinking accounted for the most cases, light and moderate drinking accounted for more than 100,000 of those cases, the study found.
Researchers have explored trends over earlier time periods in previous studies and found similar associations. But patterns of alcohol consumption—who’s drinking what and where—shift over time. While alcohol consumption is declining in some areas of the world, such as parts of Europe, it’s on the rise in other areas, including China, India, and many sub-Saharan African nations.
The types of cancer with the most cases linked to alcohol use were cancers of the esophagus and liver and, in women, breast cancer, the researchers reported July 13 in The Lancet Oncology. Eastern Asia and central and eastern Europe had the highest numbers of alcohol-related cancers in proportion to their populations, while northern Africa and western Asia had the lowest.
The WHO researchers also created an interactive website where people can explore the results by country, cancer site, and other variables.
Although awareness that drinking alcohol can cause cancer doesn’t necessarily lead people to change their behavior immediately, “knowledge is always better than no knowledge,” said Christian Abnet, Ph.D., M.P.H., of NCI’s Division of Cancer Epidemiology and Genetics. “And it’s helpful to do these studies so countries can look at their own patterns of alcohol use and decide whether they want to make some changes” in policy.
How Alcohol Boosts Cancer Risk
Drinking alcohol is strongly associated with an increased risk of certain head and neck cancers and cancers of the esophagus, liver, colon and rectum, and, in women, breast cancer. But why?
Alcohol can raise the risk of cancer in many ways. The processes that the body uses to break down alcohol produces a compound called acetaldehyde, a toxin that several organizations have classified as a probable cause of cancer in people.
Alcohol can also have more subtle cancer-promoting effects, including impairing the body’s ability to metabolize and absorb a variety of nutrients it needs to prevent cancer. It can also increase blood levels of estrogen, a sex hormone linked to breast cancer, and make the carcinogens found in tobacco smoke easier for the body to absorb.
“But only about a third of people recognize the connection between alcohol and cancer,” said Noelle LoConte, M.D., an oncologist at the University of Wisconsin–Madison and a member of the American Society of Clinical Oncology’s (ASCO) Cancer Prevention Committee who was not involved with the study. “General awareness is low, even among health care providers.”
WHO had previously released alcohol policy recommendations as part of its “best buys” campaign to help countries focus on the most effective initiatives to prevent noninfectious diseases. For alcohol-related diseases, these included higher sales taxes on alcohol, limits on where and when alcohol can be purchased, and restrictions on marketing to the public.
For example, higher sales taxes in central and eastern Europe have contributed to a drop in alcohol consumption in those regions, “and could be implemented in other world regions that do not yet have effective alcohol policies,” wrote the study’s authors, led by Harriet Rumgay from WHO’s Cancer Surveillance Branch.
Adding Precision to Risk Estimates
To better understand which regions of the world may benefit from such policy shifts, the WHO team collected country-specific estimates of cancer cases diagnosed in 2020 from the Global Cancer Observatory (GLOBOCAN) database. They combined these with recent estimates of the cancer risks associated with different levels of alcohol drinking, along with country-specific data on how much people are drinking based on age and sex.
The methods the WHO team used differ from those used in previous studies, Dr. Abnet explained. For example, instead of including all types of liver cancer, “they focused on hepatocellular carcinoma, the type of liver cancer that’s linked to alcohol,” he said.
Similarly, for esophageal cancer, the researchers zeroed in on a type called squamous cell carcinoma, which is the only type known to be triggered by alcohol consumption. “This may make the estimates of alcohol-related cancers lower than previous studies, but they’re more precise,” said Dr. Abnet.
Overall, the team found that about 741,300 cancer cases in 2020, or 4.1% of the global total for that year, could be attributed to alcohol consumption. More than three-quarters of these cases occurred in men.
Cancers of the esophagus and liver accounted for more than 340,000 alcohol-attributable cancers diagnosed in 2020. The researchers estimated that, overall, about 17% of liver cancer cases and 32% of esophageal cancer cases diagnosed in 2020 were attributable to alcohol use.
Breast cancer in women came in third place for number of cases, with almost 100,000 cases (about 4% worldwide) attributable to alcohol use. “The breast cancer numbers are pretty high, just because breast cancer is so common,” Dr. LoConte explained.
|Level of daily alcohol consumption||Estimated number of cancer cases|
|Heavy drinking (60 grams* or more)||346,400|
|Moderate-to-heavy drinking (between 20 and 60 grams)||291,800|
|Moderate drinking (20 grams or less)||103,100|
|*In measurements used in the United States, roughly 14 grams of pure alcohol (ethanol) corresponds to one standard drink (12 ounces of beer, 5 ounces of wine, or a 1.5 ounce shot of 80-proof distilled spirits (liquor).|
When the researchers analyzed moderate drinking further, they found that 41,300 of those cases could be attributed to light drinking, or consumption of 10 grams or less per day.
Overall, eastern Asia and central and eastern Europe had the highest proportions of cancer cases attributed to alcohol consumption, and northern Africa and western Asia had the lowest. Trends for women differed slightly, with the highest proportions of cancer cases attributed to alcohol consumption found in central, eastern and western Europe; Australia; and New Zealand.
Informed Choices and Policy Directions
The study had several limitations, including that it only looked at current alcohol consumption, not past drinking habits, said Dr. Abnet. Surveys worldwide often have not collected information about past alcohol use, “but for a lot of people, there’s a pattern where they drink more heavily when they’re young and moderately as they get older,” he explained.
The estimates of cancer cases attributed to alcohol may have been higher if past consumption had been accounted for, Dr. Abnet said. Ongoing surveys are now trying to capture this information, he added.
Using blood tests to get a more accurate estimate of true alcohol consumption could also benefit future research, wrote Amy Justice, M.D., Ph.D., of Yale University, in an accompanying editorial. “The sooner we start accurately measuring alcohol exposure, the sooner we can understand the true excess burden of cancer attributable to alcohol and effectively intervene,” Dr. Justice wrote.
The goal of such research isn’t to scare people who drink alcohol, said Dr. LoConte. “But right or wrong, there’s a tremendous societal fear of cancer in general. I think there is a chunk of society that, if they knew [about the risk], would drink differently,” she said.
The biggest such wins would likely come from helping heavy drinkers cut back or quit, she added. “It’s pretty clear there are no health benefits [from heavy drinking], and there’s lots of risk to health overall,” she said.
Binge drinking—consuming five or more drinks within a few hours for men or four for women—is also likely more dangerous than any other type of drinking, Dr. Abnet explained. But studies have only begun to look at the associations between binge drinking and cancer, he added.
“A lot of our surveys just estimate the total number of drinks per week and haven’t differentiated between the person who has one drink a day each week and someone who has 7 drinks just one day a week,” he said.
But although individual knowledge is important for people to make informed choices, “the ASCO committee definitely thinks policy is the way out of this problem,” said Dr. LoConte. “We need to try to use policy to make the healthier choice the easier choice.”
“We think the biggest win is to focus on youth drinking, and the [WHO “best buys”] that correlates most with less youth drinking is increasing price,” she continued. “We also think it’s important for communities—like Native communities, where alcohol use is often high—to control their own policies.”
It is important to continue studying cancers linked to alcohol, as patterns of alcohol use continue to shift over time, Dr. Abnet said. For example, in many parts of the world, women have begun drinking more than they used to, he explained. And, he added, if drinking rises within a group, their cancer cases are eventually likely to rise as well.
The COVID-19 pandemic also appears to have caused a spike in drinking among women in the United States and elsewhere, explained Dr. LoConte. “Getting access to alcohol has gotten a lot easier, with things like delivery and drive-through pickup, and women in particular are bearing a huge burden of caregiving, which has led to more drinking,” she said.
“We know from events like Hurricane Katrina and September 11th that when people drink to help cope with a very stressful, traumatic situation, they tend to sustain that drinking pattern even after the trauma abates or resolves,” she added. “So I’m guessing the same will be true with COVID, but it will be important to see globally if the same trends hold.”