How Alcohol Affects Lung Cancer Risk and Outcomes

In 2020, research from the University of Liverpool Institute of Translational Medicine strongly suggested that alcohol use disorder (AUD, a.k.a. alcoholism) is an independent risk factor of lung cancer, especially squamous cell lung carcinoma. The study contends that the same genetic variations that can predispose a person to alcohol abuse may also increase a person’s risk of lung cancer.

According to the investigators, six gene variants strongly linked to alcoholism are independently linked to lung cancer as well. Although the evidence is far from conclusive, if true, it could add lung cancer to the growing list of other cancers thought to be linked to alcohol.

Alcohol as a Carcinogen

Alcohol does more than just hurt the liver. In 2010, alcohol was classified as a carcinogen (cancer-causing agent) by the U.S. Department of Health and Human Services (HHS)—a decision that aligned with an earlier ruling from the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO).

The mechanisms for alcohol's carcinogenic effects are not entirely clear, but it is believed ethanol and its major metabolite, acetaldehyde, are genotoxic—meaning that they can damage the genetic material within a cell.

In people with a genetic predisposition for cancer, this effect may increase the speed by which tumor cells multiply by further destabilizing normal chromosomes and DNA.

Drinking Habits and Lung Cancer

Until recently, there was no clear evidence that alcohol had the same association with lung cancer as other cancers, in part because many drinkers are smokers (making it hard to draw a clear cause-and-effect relationship). Moreover, of the studies that did exist, most were relatively small and often came to contradictory conclusions.

The link between lung cancer and alcohol consumption has long been considered controversial. There has been debate about the nature of this relationship, with some studies arguing that there is no association and others contending that alcohol may have a protective benefit in certain cases.

One of the largest analyses, published in 2016 in the American Journal of Epidemiology, reported that heavy alcohol use (defined as over seven drinks per day) modestly increased the risk of lung cancer, but that moderate consumption (one drink or less per day) actually decreased the risk.

This is not all that unusual a finding given that similar patterns are seen with other types of cancers. That is, low alcohol consumption appears to have a protective benefit while high consumption increases the cancer risk.

Where lung cancer diverges is in the high rate of smoking among heavy drinkers. While 29.8% of non-drinkers in the study were never-smokers, 30.3% of heavy drinkers were current or former smokers who smoked more than 20 cigarettes per day. As such, it is difficult to ascertain how much heavy drinking contributes to the risk among people who are already at high risk due to smoking.

With that said, lung cancer can occur in drinkers who have never smoked. According to a 2015 review in the Permanente Journal, heavy alcohol consumption (over three drinks per day) increases the risk of lung cancer in never-smokers by 30%.

What this suggests is that alcohol may contribute to the development of lung cancer independently, most presumably in people with a genetic predisposition for the disease.

Genetic Predisposition

Lung cancer is a complex disease brought on by numerous intersecting factors, including genetics, environment, and lifestyle. Heavy drinking as an independent risk factor is believed to fit somewhere in the genetic puzzle, although it is unclear if heavy drinking is the cause or the effect.

In the aforementioned study from the University of Liverpool, scientists decided to look at the genes associated with alcohol use disorder and found a surprising link to the rate of lung cancer in 171,216 adults in the United Kingdom.

Alcoholism is believed to be strongly influenced by mutations of the alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) genes, both of which direct how alcohol is metabolized and indirectly influence reward pathways in the brain.

Mutations of ADH and ALDH can increase the speed by which alcohol is broken down while increasing the concentration of the "feel-good" hormone dopamine in the brain. These effects can predispose a person to AUD. Other genes—ADH1B, GCKR, SLC39A8, and KLB—are also linked to alcohol use disorder.

What this suggests is that having a genetic predisposition for AUD may predispose you to lung cancer as well.

Even so, having these genetic variants neither means you will get lung cancer nor develop alcoholism; the relationship is not so straightforward. It is only in the presence of AUD that the risk of lung cancer appears to increase.

As such, alcohol may trigger AUD in people with a predisposition for the disease and, in turn, promote the progression of lung cancer along the same genetic pathways. It is a compelling hypothesis in need of further research.

Alcohol Use and Lung Cancer Survival

Research also suggests that alcohol use can influence morbidity and mortality (illness and death) in people with lung cancer. Contributing to this phenomenon is a person's perception of wellness following cancer treatment.

According to a review of studies from the Mayo Clinic College of Medicine, around 69% of people with lung cancer were drinkers prior to their diagnosis. Of these, 16% quit alcohol following cancer treatment. Those who didn't were nine times more likely to describe themselves as being in poor health compared to those who did.

A 2018 study in the Journal Thoracic Disease further reported that around one in eight people requiring lung cancer surgery has AUD, a condition that almost invariably leads to serious health complications.

A Word From Verywell

Despite ongoing debate and gaps in research, it seems clear that heavy drinking is something that needs to be addressed if you are at risk of lung cancer. While there is nothing to suggest that alcohol causes lung cancer outright, the statistics strongly suggest that heavy drinkers are more likely to develop the disease—even if they don't smoke.

Like cigarettes, there is no actual benefit to drinking. And, it's well known that quitting alcohol can be as hard for some as quitting cigarettes. If you have signs and symptoms of AUD, you need to seek treatment, whether you are at risk of cancer or not.

Furthermore, despite evidence that light to moderate drinking is associated with a lower risk of lung cancer, this should in no way suggest that a couple of glasses of alcohol per week "prevents" cancer. It does not.