October 8, 2012 (Vienna, Austria) — The link between light to moderate alcohol consumption and an increased risk for cancer might be largely due to underreporting.
A large American cohort study has found that a substantial portion of the apparent increased risk for cancer among light to moderate drinkers is related to people lying about their drinking habits, according to study author Arthur Klatsky, MD, from Kaiser Permanente Medical Center, Oakland, California, who presented the results here at the 2012 European Society for Medical Oncology Congress.
Although this analysis is "inferentially," it is probably applicable to most other studies, he noted.
There is evidence that heavy alcohol consumption is related to an increased risk for several types of cancer, he explained during a press briefing. "However, the role of light to moderate drinking is less clear and the results of studies differ," Dr. Klatsky said. "There have been various kinds of statements that have come out, which I think are frightening to people, that say there is no level of alcohol consumption that is safe. Some studies suggest that any amount of drinking can increase the risk of cancer," he noted.
Heavy drinking has been associated with many health risks, he said, but light drinking might be beneficial for some people. "The idea that light drinking can increase cancer risk is very important from a public health standpoint," Dr. Klatsky explained. He added that "many people underestimate the amount that they drink."
A number of studies have assessed the relation between alcohol intake and cancer risk, and some suggest that any alcohol can boost the risk of developing cancer. A recent meta-analysis of 113 studies that looked at light drinking and breast cancer concluded that women should not drink more than 1 alcoholic beverage a day. "A significant increase in the order of 4% in the risk of breast cancer is already present at intakes of up to 1 alcoholic drink per day," note the meta-analysis researchers, who were led by Helmut K. Seitz, PhD, from the Centre of Alcohol Research at the University of Heidelberg in Germany.
Results from the Million Women Study conducted in the United Kingdom found that each alcoholic drink consumed significantly increased the risk for cancer. Among women living in industrialized nations, those researchers estimated a background incidence of 118 cancers diagnosed per 1000 women up to the age of 75 years. Consuming 1 drink per day increased this risk to an extra 15 cancers per 1000 women, and 2 drinks a day increased it to an extra 30 cancers per 1000 women.
Alcohol consumption appears to be strongly and dose-dependently linked to colorectal cancer risk. Another meta-analysis found moderate alcohol consumption to be associated with a 21% increase in colorectal cancer, and heavy drinking (at least 4 drinks/day) to be associated with a 52% increased risk.
Individual Advice Needed
For their study, Dr. Klatsky and colleagues used a database that supplied baseline alcohol status for 129,987 people at routine health examinations in California from 1978 to 1985. Analyses were performed for the risk for all cancers and for a subset of 5 types with alcohol-associated risk (upper airway digestive, liver, breast, lung, colorectal). They controlled for confounders, including age, sex, ethnicity, smoking, education, and body mass index; alcohol used was evaluated categorically, and lifelong abstainers were used as the reference group.
Compared with abstainers, alcohol-associated increased cancer risk was 17% for exdrinkers (P < .001), 9% for those who drank less than 1 drink per day (P = .04), 9% for those who drank 1 to 2 drinks per day (P < .001), and 16% for those who drank 3 or more drinks per day (P < .01).
The relation between light to moderate drinking (less than 3 drinks per day) and cancer risk were similar in men and women and among ethnic subgroups.
Dr. Klatsky and his team stratified individuals according to suspicion of underreporting alcohol intake. People were "suspicious" if they had ever reported heavy drinking or had an alcohol-related diagnoses.
The relative risk for cancer among suspicious people who reported consuming 1 to 2 drinks per day was 1.14 (95% confidence interval [CI],1.04 to 1.25; P = .004), whereas for nonsuspicious people, it was 1.00 (95% CI, 0.89 to 1.11). For suspicious people who reported consuming less than 1 drink per day, the relative risk was 1.17 (95% CI, 1.06 to 1.28; P = .001); for nonsuspicious people, it was 1.00 (95% CI, 0.90 to 1.09).
For the alcohol-related composite, the relative risk for suspicious people who reported consuming 1 to 2 drinks per day was 1.41 (95% CI, 1.23 to 1.62); for suspicious people, it was 1.06 (95% CI, 0.89 to 1.25). For suspicious people who reported consuming less than 1 drink per day, the relative risk was 1.39 (95% CI, 1.21 to 1.59; P < .00); for nonsuspicious people, it was 1.03 (95% CI, 0.90 to 1.18).
The authors conclude that a substantial portion of the apparent increased risk for cancer among light to moderate drinkers is related to underreporting. However, Dr. Klatsky cautioned that "one observational study does not establish causality."
Advice to the public as far as alcohol and cancer risk "needs to be individualized," he said, noting that the "overall picture and personal factors" need to be considered.
2012 European Society for Medical Oncology (ESMO) Congress: Abstracts 1459 and 1421. Presented September 30, 2012.
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