From Medscape Medical News
Laurie Barclay, MD
August 25, 2010 — Alcohol use is linked to a risk for hormone-sensitive breast cancers, according to results from the Women's Health Initiative (WHI) Observational Study reported Online First August 23 and to appear in the September 22 print issue of the Journal of the National Cancer Institute.
"Alcohol consumption is a well-established risk factor for breast cancer," write Christopher I. Li, MD, PhD, from Fred Hutchinson Cancer Research Center in Seattle, Washington, and colleagues. "This association is thought to be largely hormonally driven, so alcohol use may be more strongly associated with hormonally sensitive breast cancers. Few studies have evaluated how alcohol-related risk varies by breast cancer subtype."
As part of the prospective WHI, the goal of this analysis was to determine the association between self-reported alcohol intake and the risk for postmenopausal breast cancer. Of 87,724 participants enrolled from 1993 through 1998, a total of 2944 were diagnosed with invasive breast cancer during follow-up through September 15, 2005.
Based on multivariable adjusted Cox regression models used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs), along with 2-sided statistical tests, alcohol intake was directly associated with an overall risk for invasive breast cancer, invasive lobular carcinoma, and hormone receptor-positive tumors (for all, P trend ≤ .022).
The association between alcohol intake and breast cancer was stronger for certain types of invasive breast cancer than for others.
The risk for hormone receptor-positive invasive lobular carcinoma in women who drank at least 7 alcoholic beverages per week was nearly double that in never-drinkers (HR, 1.82; 95% CI, 1.18 - 2.81), but the risk for hormone receptor-positive invasive ductal carcinoma was not statistically significantly increased (HR, 1.14; 95% CI, 0.87 - 1.50). The difference in HRs per drink per day among current drinkers was 1.15 (95% CI, 1.01 - 1.32; P = .042).
Absolute rates of hormone receptor-positive lobular cancer were 5.2 per 10,000 person-years among never-drinkers and 8.5 per 10,000 person-years among current drinkers. For hormone receptor-positive ductal cancer, absolute rates were 15.2 and 17.9 per 10,000 person-years, respectively.
"Alcohol use may be more strongly associated with risk of hormone-sensitive breast cancers than hormone-insensitive subtypes, suggesting distinct etiologic pathways for these two breast cancer subtypes," the study authors write.
Limitations of this study include observational design with possible residual confounding, and assessment of alcohol use only at baseline, so that extensive measurement errors or changes in alcohol use could affect the study conclusions. In addition, data on tumor characteristics were based on information abstracted from local pathology reports, which may have led to an unknown degree of misclassification because of variations in histology and hormone-receptor assessment across the United States.
"[T]his study provides prospective evidence that the relationship between alcohol use and breast cancer risk varies by breast cancer subtype, with risks most pronounced for invasive lobular and hormone receptor–positive tumors," the study authors conclude.
"Hence, alcohol is another established breast cancer risk factor that appears to be differentially associated among breast cancer subtypes, and this pattern of associated risks indicates that tumors defined by both histology and hormone receptor status have somewhat different etiologic determinants. These findings highlight the importance of incorporating breast cancer subtype information in etiologic studies of the disease."
This work was supported by the WHI program, which is funded by the National Heart, Lung, and Blood Institute, National Institutes of Health, US Department of Health and Human Services. The study authors have disclosed no relevant financial relationships.
J Natl Cancer Inst. Published online August 23, 2010.
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