Consistent heavy alcohol consumption across adulthood is associated with a substantially higher risk of colorectal cancer, according to new findings from a large US cancer screening trial.
The study
Published online in CANCER, a peer-reviewed journal of the American Cancer Society, the research examined how lifetime drinking patterns influence colorectal cancer risk — suggesting that quitting may reduce that risk over time.
Researchers analysed data from 88,092 adults enrolled in the National Cancer Institute (NCI) Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial.
Participants were cancer-free at baseline and followed for more than 20 years, during which time 1679 cases of colorectal cancer were diagnosed.
Results
The study found that current drinkers with an average lifetime alcohol intake of 14 or more drinks per week (heavy drinkers) had a 25% higher risk of developing colorectal cancer and a 95% higher risk of developing rectal cancer compared with those with an average lifetime alcohol intake of less than 1 drink per week (light drinkers).
Drinking patterns across adulthood also matter.
The study found that individuals who drank heavily throughout adult life had a 91% higher risk of colorectal cancer compared with those who consistently consumed low levels of alcohol.
In contrast, no evidence of increased colorectal cancer risk was observed among former drinkers, and former drinkers had lower odds of developing non-cancerous colorectal tumours, or adenomas (which may go on to become cancerous) than current drinkers, averaging less than 1 drink per week.
This suggests that alcohol cessation may lower individuals’ risks, although the authors note that these data were limited.
Biological mechanisms
The association between alcohol consumption and increased risks observed in this and other studies might be explained by carcinogens produced from alcohol metabolism or alcohol’s effects on gut microbes.
Additional studies are needed to test whether these mechanisms are involved.
“Our study is one of the first to explore how drinking alcohol over the life course relates to both colorectal adenoma and colorectal cancer risk.
“While the data on former drinkers were sparse, we were encouraged to see that their risk may return to that of the light drinkers,” says co–senior author Erikka Loftfield, PhD, MPH, of the NCI, part of the National Institutes of Health.
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