Originally published as JCO Early Release 10.1200/JCO.2009.21.3371 on February 23 2009

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Alcohol Consumption and Breast Cancer Survival

Division of Surgical Oncology, The Cancer Institute of New Jersey and Robert Wood Johnson Medical School, New Brunswick, NJ

To the Editor:

We read with great interest the paper by Barnett et al, ¹ recently published in Journal of Clinical Oncology, in which they evaluated whether several risk factors known to affect breast cancer risk also played a role on breast cancer survival using data from the Studies of Epidemiology and Risk Factors in Cancer Heredity (SEARCH) breast cancer study, an ongoing population-based study. Their claim of an "apparent benefit of alcohol intake not described before" attracted our attention, as there is strong evidence linking alcohol consumption to increased breast cancer risk.^2–4 The authors mentioned that caution should be used in the interpretation of their data, and indeed, there are several concerns with the presentation and interpretation of their findings.

The manuscript lacks details concerning how alcohol consumption was ascertained and, more importantly, what time frame was used in eliciting intake. Current intake in the context of a case-control study or a cohort study of healthy participants typically refers to alcohol consumption before diagnosis. In the context of a cohort study of breast cancer survivors, current intake could fall in the time period before, during, or after treatment. Clearly, the impact of intake during each one of these time frames may be different and needs to be specified.

Follow-up seemed to have been limited to ascertaining vital status and, therefore, the outcome under investigation was total mortality and not breast cancer mortality or disease-free survival. In that sense, the title of the manuscript is misleading, as the study did not evaluate survival from the disease but overall mortality. In that moderate alcohol consumption has been associated with lower overall and coronary heart disease–related mortality in women,⁵ the apparent reduced total mortality among drinkers of at least seven units per week could be due to a reduction in cardiovascular mortality. Ultimately, the authors compared total mortality in patients with breast cancer who reported drinking more than seven units per week (roughly one drink by American standards) with mortality in those drinking less. Therefore, the impact of abstaining from alcohol was not evaluated.

It should be noted that the reduction of 2% in the risk of death per unit of alcohol per week reported in the abstract was based on univariate analyses. With adjustment for stage, grade, age, and estrogen receptor status, the association was attenuated and no longer statistically significant (HR: 0.84; 95% CI, 0.63 to 1.12). Furthermore, failure to adjust for treatment information makes the interpretation of results difficult, especially since alcohol intake was found to vary with tumor stage, and choice of adjuvant therapies also varies with stage. The study also failed to adjust for other important covariates such as physical activity or body mass index, which have been related to breast cancer mortality.³

In comparing their findings with those of other studies, Barnett et al¹ mentioned that the study by McDonald et al⁶ had previously reported an inverse association between alcohol intake and breast cancer survival, while other studies did not support that. In the study by McDonald et al, consumption of at least one drink per week before diagnosis was associated with a 2.7-fold increase in risk of death (95% CI, 1.3- to 5.8-fold), after adjusting for cigarette smoking, tumor stage, and treatment. Overall, the role of alcohol consumption in breast cancer survival has been evaluated in only a few studies, with findings too inconsistent to allow any recommendations.⁷ Most of these studies had limited power due to a small number of events (recurrences or deaths) and/or drinking range, and some of them failed to control for important prognostic factors, such as stage at diagnosis and treatment. The effect of heavy alcohol use on breast cancer prognosis has not been evaluated. Overall, there is currently insufficient evidence to conclude that drinking has no effect on cancer survival.

In summary, the study by Barnett et al¹ provided little evidence that drinking alcohol after a diagnosis of breast cancer is safe. Based on the currently available evidence, patients with breast cancer should be made aware that alcohol has been shown consistently to increase the risk of developing breast cancer and other cancers,^2,3 whereas its impact on breast cancer survival remains uncertain.

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The author(s) indicated no potential conflicts of interest.

REFERENCES

1. Barnett GC, Shah M, Redman K, et al: Risk factors for the incidence of breast cancer: Do they affect survival from the disease? J Clin Oncol 26:3310–3316, 2008.[Abstract/Free Full Text]

2. Kushi LH, Byers T, Doyle C, et al: American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention: Reducing the risk of cancer with healthy food choices and physical activity. CA Cancer J Clin 56:254–281, 2006.[Abstract/Free Full Text]

3. World Cancer Research Fund. American Institute for Cancer Research: Food, Nutrition, and the Prevention of Cancer: A Global Perspective. Washington, DC: American Cancer Institute for Cancer Research, 2007. p.157–390.

4. Bandera EV, Kushi LH. Alcohol and cancer. D Heber, GL Blackburn, VLW Go, et al. Nutritional Oncology, ed 2 San Diego, CA: Academic Press, 2006. p.219–272.

5. Thun MJ, Peto R, Lopez AD, et al: Alcohol consumption and mortality among middle-aged and elderly US adults. N Engl J Med 337:1705–1714, 1997.[Abstract/Free Full Text]

6. McDonald PA, Williams R, Dawkins F, et al: Breast cancer survival in African American women: Is alcohol consumption a prognostic indicator? Cancer Causes Control 13:543–549, 2002.[CrossRef][Medline]

7. Doyle C, Kushi LH, Byers T, et al: Nutrition and physical activity during and after cancer treatment: An American Cancer Society guide for informed choices. CA Cancer J Clin 56:323–353, 2006.[Abstract/Free Full Text]

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