(ChemotherapyAdvisor) – Consuming a glass or less of alcohol a day ups certain cancer risks and accounts for as many as 34,000 cancer deaths a year worldwide, report Italian researchers in the Annals of Oncology.

“Convincing evidence” already exists that moderate to heavy alcohol consumption increases the risk of cancers of the colorectum, breast, larynx, liver, esophagus, oral cavity, and pharynx, reported lead author Vincenzo Bagnardi, PhD, Department of Statistics, University of Milan-Bicocca, Milano, Italy. Approximately 5.2% of men’s cancers and 1.7% of women’s cancers are attributable to alcohol drinking, Bagnardi’s team reported.

However, cancer risks for individuals who imbibe lightly — those who drink 1 or fewer alcoholic beverages (≤12.5 g ethanol) a day — have not been as well analyzed. So the team analyzed data pooled from 222 studies that included 92,000 cancer patients who were light drinkers, and another 60,000 nondrinker cancer patients. Compared to nondrinkers, light alcohol consumption was associated with elevated risks of oropharyngeal cancer (relative risk [RR] = 1.17; 95% confidence interval [CI], 1.06–1.29), esophageal squamous cell carcinoma (SCC; RR = 1.30; 95% CI, 1.09–1.56) and female breast cancer (RR = 1.05; 95% CI, 1.02–1.08).

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“We estimated that ~5,000 deaths from oropharyngeal cancer, 24,000 from esophageal SCC, and 5,000 from breast cancer were attributable to light drinking in 2004 worldwide,” Bagnardi and his coauthors reported. “No association was found for colorectum, liver, and larynx tumors” for light drinking.

The meta-analysis included case-control and cohort studies published as original papers; data from abstracts, letters, reviews, and previous meta-analyses were not used, the team wrote. Studies were included if they reported odds ratios, relative risks, or hazard ratios, or the data with which those could be calculated for light drinkers and nondrinkers. Studies that reported on specific alcoholic beverages (for example, patients reporting that they drink only beer) were not included because of possible underreporting of consumption of other alcoholic beverages, the team reported.