Higher lifetime alcohol consumption is linked to a higher risk of colorectal cancer, with the strongest association seen for rectal cancer, according to new research published in the journal Cancer.
The findings add to evidence that alcohol is a cancer risk factor and suggest that long-term drinking patterns across adulthood may matter, while quitting alcohol may reduce certain risks linked to precancerous growths.
What the study found
The research analyzed U.S. adults in the National Cancer Institute’s Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial who did not have cancer at the start of the study.
In the EurekAlert summary, investigators reported 1,679 colorectal cancer cases among 88,092 participants over 20 years of follow-up.
ABC News, reporting on the same study, described following more than 88,000 adults with no prior cancer history and tracking outcomes for nearly a decade, a difference in follow-up time compared with the EurekAlert release.
Researchers compared people who averaged fewer than one drink per week over their lifetime with people who averaged at least 14 drinks per week, which the release described as heavy drinking.
Among current drinkers, those averaging at least 14 drinks per week over their lifetime had a 25% higher risk of developing colorectal cancer than people averaging fewer than one drink per week.
The link appeared stronger for rectal cancer: the EurekAlert release reported a 95% higher rectal cancer risk for heavy lifetime drinkers compared with light drinkers, while ABC News described the rectal cancer risk as nearly doubled.
The study also examined how consistent drinking patterns were across adulthood.
People who drank heavily throughout adulthood had a 91% higher risk of colorectal cancer compared with people who consistently drank lightly, according to both the EurekAlert release and ABC News coverage.
Former drinkers and adenomas
In the EurekAlert release, researchers reported no evidence of increased colorectal cancer risk among former drinkers.
The release also said former drinkers had lower odds of developing noncancerous colorectal tumors called adenomas than current drinkers who averaged fewer than one drink per week, while noting the data on former drinkers were limited.
ABC News similarly reported that heavy drinking was not strongly linked to adenoma risk, but that people who quit drinking had significantly lower odds of developing nonadvanced adenomas compared with light drinkers.
Co–senior author Erikka Loftfield of the National Cancer Institute said the study is among the first to examine alcohol intake over the life course in relation to both colorectal adenoma and colorectal cancer risk.
Loftfield also said the researchers were encouraged to see that former drinkers’ risk “may return to that of the light drinkers,” while also emphasizing that former-drinker data were sparse.
Why rectal cancer stood out
Across the reporting and the release, the strongest signal appeared in rectal cancer.
ABC News quoted Dr. Jeffrey Farma, a colorectal cancer specialist, saying rectal cancer is “often more difficult to treat and more involved clinically,” making screening and early identification especially important.
ABC News also quoted Dr. Fola May, a GI specialist and associate director of the UCLA Kaiser Permanente Center for Health Equity, saying, “We’re seeing an uptick in rectal cancers,” and adding that researchers need to understand why alcohol may affect the lower colon differently.
While the release did not assign a single cause, it said the observed association between alcohol and increased risk could potentially be explained by carcinogens produced during alcohol metabolism or alcohol’s effects on gut microbes, and it called for additional studies to test these mechanisms.
What doctors say about screening
ABC News quoted Dr. Lynn M. O’Connor, section chief of colon and rectal surgery at Mercy Medical Center and St. Joseph Hospital in New York, saying, “The longer someone drinks, the longer their colon and rectum are exposed damage and impaired repair, both major mechanisms of cancer.”
ABC News also quoted May saying, “These numbers are not guarantees, but signals to do something before it’s too late,” and added her point that colorectal cancer is one of the cancers that can be prevented or caught early, but fewer than 70% of eligible people get screened.
In the same report, colorectal screening was described as recommended for all adults starting at age 45, citing the United States Preventative Services Task Force.
The report listed screening tools that include annual stool tests, CT scans every five years, or colonoscopies every 10 years.
May was also quoted urging people not to delay screening, saying, “Everyone should be screened. It saves lives, and people are dying unnecessarily when they put it off.”
ABC News further reported that some people at higher risk may need screening earlier or more often, and quoted Farma advising evaluation for symptoms such as bleeding or persistent bowel habit changes, even in someone in their 30s with prolonged heavy drinking.
