Critique 085: Moderate alcohol intake is associated with a lower risk of kidney cancer — 19 July 2012

Song DY, Song S, Song Y, Lee JE.  Alcohol intake and renal cell cancer risk: a meta-analysis.  British Journal of Cancer 2012;106:1881–1890.

Authors’ Abstract

BACKGROUND: An inverse association between alcoholic beverage intake and risk of renal cell cancer has been suggested in recent studies.

METHODS: We examined the association between alcoholic beverages and renal cell cancer risk in a meta-analysis.  We identified relevant studies by searching the database of PubMed, EMBASE, and MEDLINE published through August 2011.  We combined the study-specific relative risks (RRs) using a random-effects model.

RESULTS: A total of 20 case–control studies, 3 cohort studies, and 1 pooled analysis of cohort studies were included in the metaanalysis.  We observed that alcoholic beverage intake was associated with a lower risk of renal cell cancer in combined analysis of case–control and cohort studies; for total alcoholic beverage intake, combined RRs (95% confidence intervals) comparing top with bottom categories were 0.76 (0.68–0.85) in case–control studies, and 0.71 (0.63–0.78) in cohort studies (P for difference by study design=0.02).  The inverse associations were observed for both men and women and for each specific type alcoholic beverage (beer, wine, and liquor).  Also, we found that one drink per day of alcoholic beverage conferred the reduction in renal cell cancer risk, but further drinking above that level did not add benefit.

CONCLUSION: The findings from our meta-analysis support the hypothesis that alcoholic beverage intake is inversely associated with the risk of renal cell cancer, with moderate consumption conferring the protection and higher consumption conferring no additional benefits.

Forum Comments

Background:  In an earlier large pooled analysis by Lee et al,¹ a 20-30% lower risk of renal cell (kidney) cancer was seen among drinkers of 5 grams/day or more of alcohol.  For consumers of ³ 15 g/day (approximately 1 to 2 typical drinks), the RR was 0.72, a 28% lower risk than that of nondrinkers.  A reduced RR was seen for all alcoholic beverages, with lower risks associated with the consumption of up to 1 drink/day of beer (-13%), wine (-28%), and liquor (-12%).  Other large recent studies included in the present meta-analysis were those of Setiawan et al,² Lew et al,³ and the report from Allen et al⁴ from the Million Women’s study.

Comments on the present paper:  This paper is a straight-forward meta-analysis of the association of alcohol consumption with the risk of renal cell cancer; it supports previous findings of a lower risk of such cancer among moderate drinkers than among abstainers.¹  In fact, several Forum reviewers believed that this analysis presents nothing new, stating that this inverse association between alcohol and kidney cancer has been known for some time.  Still, this large meta-analysis is useful as it is based on 13,819 cases of renal cell cancer and 1,537 incident kidney cancer cases from studies in North America and Europe.  The referent category chosen by the authors included never drinkers, non-drinkers, and those reporting 0-1 drinks/day, low to 1 cup per week, or < 1drink/week; thus it included never drinkers and occasional or rare drinkers.

As stated by the authors, the findings of a lower risk of renal cancer among moderate drinkers were much more consistent in cohort studies than in case-control studies.  In the prospective cohort studies included in this analysis, most showed 25% or more reduction in risk, while case-control studies showed much more variability.  A meta-analysis of prospective studies is an important aspect of the present paper.

Forum members agreed that while the association of alcohol with a lower risk of renal cell cancer is not new, there are major strengths of the present study: the large number of cases, the consistency between cohort and case control studies, and the cubic spline analyses showing a dose-response relation. 

Risk factors for kidney cancer:  The recognized risk factors for renal cancer are smoking, obesity, and hypertension.  In the present meta-analysis, results from studies adjusting for one or more of these factors showed similar effects of alcohol on renal cancer risk as did unadjusted analyses.  There were very similar effects for beer, wine, and spirits, suggesting that ethanol is the important factor for these effects.  Essentially all of the lowering of risk was apparent at about 1 drink/day, and there was little further effect from greater amounts of alcohol reported by subjects (although the number of heavier drinkers in this meta-analysis was very small). 

Mechanisms:  The mechanism by which moderate alcohol consumption may lower the risk of renal cancer is not known.  The authors suggest that alcoholic beverages may reduce the risk of renal cancer through an improvement in insulin resistance or from alcohol’s beneficial effects on vascular function.  One Forum reviewer points out that, of necessity, all of these studies on alcohol and cancer are observational studies (with self-reported alcohol intake), and it remains unclear how ethanol causes a reduction in the risk of renal cancer.

References

1.  Lee JE, Hunter DJ, Spiegelman D, Adami H-O, Albanes D . . .  Smith-Warner SA.  Alcohol intake and renal cell cancer in a pooled analysis of 12 prospective studies.  J Natl Cancer Inst 2007;99:801–810.

2.  Setiawan VW, Stram DO, Nomura AM, Kolonel LN, Henderson BE.  Risk factors for renal cell cancer: the multiethnic cohort.  Am J Epidemiol 2007;166:932–940.

3.  Lew JQ, Chow WH, Hollenbeck AR, Schatzkin A, Park Y.  Alcohol consumption and risk of renal cell cancer: the NIH-AARP diet and health study. Br J Cancer 2011;104:537–541.

4.  Allen NE, Beral V, Casabonne D, Kan SW, Reeves GK, Brown A, Green J; on behalf of the Million Women Study Collaborators.  Moderate alcohol intake and cancer incidence in women.  J Natl Cancer Inst 2009;101:296–305.

Forum Summary

A majority of previous epidemiologic studies have shown that moderate drinking is associated with a lower risk of kidney cancer, which may affect about 1% of the general population.  In published prospective cohort studies, the risk for such cancer among moderate drinkers is usually about 25% less than the risk seen among non-drinkers. 

This well-done meta-analysis supports these findings: for the more-reliable prospective cohort studies (rather than case-control studies) the current study finds a 29% lower risk for subjects in the highest category of alcohol consumption in comparison with subjects in the lowest alcohol category.  The findings suggest similar effects among men and women, and for all types of alcohol beverages.  The effects are seen at a level of about one drink/day, with little further reduction in risk for greater alcohol consumption. 

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Comments on this critique were provided by the following members of the International Scientific Forum on Alcohol Research:

Harvey Finkel, MD, Hematology/Oncology, Boston University Medical Center, Boston, MA, USA

Andrew L. Waterhouse, PhD, Marvin Sands Professor, Department of Viticulture and Enology, University of California, Davis; Davis, CA, USA

Erik Skovenborg, MD, Scandinavian Medical Alcohol Board, Practitioner, Aarhus, Denmark

Luc Djoussé, MD, DSc, Dept. of Medicine, Division of Aging, Brigham & Women’s Hospital and Harvard Medical School, Boston, MA, USA 

Arne Svilaas, MD, PhD, general practice and lipidology, Oslo University Hospital, Oslo, Norway

R. Curtis Ellison, MD, Section of Preventive Medicine & Epidemiology, Boston University School of Medicine, Boston, MA, USA